GC-43: Fix Python 3.11 failing CLI test due to subparser masking:

- Renamed the subparser commands to be fully distinct.
- The subparser registration is never reset since the Python test file
is run as part of a single process, thus the two tests would
register two subparsers under the same subcommand.
- In older versions of Python this was not a problem, but with newer
verions (3.11+) this inconsistency has been fixed. For more details,
see:

https://bugs.python.org/issue39716

GC-45: Update copyright information:

- Changes to code base were previously done in 2020 as well (based on
git history).

GC-37: The --csr and --key-specification options should be exclusive:

- Updated list of invalid invocations in the unit tests.
- Updated parsers for server and client subcommands.

GC-37: Deduplicate additional tests for validation of CLI arguments:

- Merge the tests for invoking commands without mandatory positional
arguments into test for invalid CLI invocations.
- Merge the tests for invoking renew commands with conflicting
positional arguments into test for invalid CLI invocations.

GC-37: Added ECDSA support for issuing client certificates via client command:

- Added functional test.
- Updated unit tests.
- Expose ECDSA key specification in the client command help.

GC-37: Added ECDSA support for issuing server certificates via server command:

- Added functional test.
- Added unit tests.
- Updated existing functional test that checks for avertising of curve
support for key specification in the init command to be a bit less
fragile in case the output gets broken-up into different lines in a
slightly different location.
- Implement ability to get public key specification out of ECDSA
public key.
- Expose ECDSA key specification in the server command.
- Updated inline documentation.

GC-37: Added ECDSA support for initialising CA hierarchy:

- Added functional test.
- Added unit tests.
- Updated key specification parsing to support ECDSA specification
using curve name.
- Updated KeyGenerator to handle ECDSA private keys generation.
- Updated inline documentation.

GC-37: Added support for requesting custom RSA key size when renewing:

- Added functional test.
- Added unit tests.
- Updated existing functional test for renew command help to cope with
addition of one more option (output lines from help changed).
- Added new CLI option for passing-in key specification, used in
combination with the --new-private-key option.
- Renew command function now accepts key specification
parameter. Updated existing code and tests accordingly for the new
function signature.
- If key specification is not passed-in and new private key is
requested, key size is extracted from existing artefacts (e.g. it
does not use CA hierarchy's key size).

GC-37: Added support for requesting custom RSA key size when issuing client certificates:

- Added functional test.
- Added unit tests.
- Added new CLI option to the client command.
- Updated the client command to use the passed-in key specification.
- Updated existing tests to cope with changes to the client command
function signature.
- Fixed small typo in docstring for the server command.
- Fixed functional test for client command help that expected
positional argument in a specific line.

GC-37: Added support for requesting custom RSA key size when issuing server certificates:

- Added functional test.
- Added unit tests.
- Added new CLI option to the server command.
- Updated the server command to use the passed-in key specification.
- Updated existing tests to cope with changes to the server command
function signature.

GC-37: Refactor key specification handling:

- Perform the key specification parsing within CLI module itself,
don't do it via crypto module.
- Pass-in tuple consisting out of algorithm and associated parameters
into the init command instead of key generator.
- Updated all tests to accomodate the change in init function
signature.
- Simplify the KeyGenerator class.
- Do not test if KeyGenerator class sets the properties via
constructor - it is sufficient to test string represenation and key
generation.

GC-37: Added support for requesting custom RSA key size when initialising the CA hierarchy:

- Added functional test.
- Added unit tests.
- Added new CLI option for specifying the algorithm.
- Implemented KeyGenerator factory-like class that can be called to
generate a private key with desired specification.
- The init init function now accepts a callable that is used to
generate private keys.
- The generate_ca_hierarchy function now accepts a callable that is
used to generate private keys.
- Updated existing unit tests to cope with changes to the init
and generate_ca_hierarchy function signatures.
- Updated existing unit tests to cope with changes to existing
functionality.
- Updated existing functional tests to cope with changes in command
output.

GC-23: Removed option to update DNS names from server command:

- Removed functional test.
- Dropped the option from CLI.
- Dropped the option from command function implementation.
- Updating code for new command function signature.
- Updated existing unit tests.
- Removed unneeded unit tests.

GC-23: Implemend option for updating DNS names for renew command:

- Added functional test covering the new functionality.
- Implemented ability to accept new DNS names in the renew command.
- Updated existing unit tests for new function signature.
- Added unit tests covering the new functionality.

Noticket: Compatibility fixes for Python 3.4:

- Fixed invocation of pexepect.spawnu to convert the passed-in
arguments explicitly into a list. Necessary since Python 3.4 can't
use the *args construct outside of assignment.
- Updated the certificate_to_pem function to return str instead of
bytes. Necessary since Python 3.4 does not support things like b"%s"
% mybytes.
- Fixed test for existence of help CLI command. Previous code was
referencing a wrong/non-existent function help (the actual name has
to be help_ in order not to shadow the built-in function).
- Updated unit test invocations that use the read_certificate
function.
- Updated tests for the read_certificate function.

GC-22: Updated renew command to replace existing private key with CSR if passed-in:

- Added functional test which covers renewal of server and client
certificates using CSR when previous certificate was issued using
private key.
- Replaced the private key with CSR when renewing certificate using
CSR in case where previous certificate was issued with private key.
- Updated signature for renew command to accept path to custom CSR.
- Updated existing unit tests for new renew command signature.
- Added unit tests covering new functionality.

GC-22: Implemented issuance of server certificates using passed-in CSR:

- Added functional test.
- Expanded server command to accept path to custom CSR file and handle
it appropriatelly.
- Updated existing unit tests to fix command server invocation.
- Added new unit tests.

GC-22: Implemented issuance of client certificates using passed-in CSR:

- Added functional test covering the issuance of client certificate
using CSR.
- Updated default value for the CSR client command option to be
explicitly None.
- Updated the client command to take in the CSR as an argument and
process it accordingly.
- Added helpers for generating CSR, as well as writing and reading
them to/from file.
- Updated existing tests to use new signature for the client
command.
- Added new unit tests for implemented functionality.

GC-22: Added options to parser for accepting CSR for issuing/renewing certificates:

- Implemented functional test for verifying option availability.
- Added CSR option to server, client, and renew commands.
- Make the new CSR option and --new-private-key option exclusive with
each other.

GC-20: Show informative message when calling status command on uninitialised directory:

- Added small function test to cover the scenario when status command
is called on an uninitalised directory.
- Updated the status command implementation.
- Implemented the necessary unit tests.

GC-20: Added initial dummy implementation of status command:

- Added functional test checking if the command is available and has
help.
- Updated unit tests for new CLI command.
- The command does not do anything at the moment.

Noticket: Deduplicate testing of functions that set-up subcommand parsers:

- Updated the CLI tests.
- Introduced parametrized tests for checking return object of set-up
subcommand parser functions (will go through all registered
functions).
- Introduced parametrized test for checking if functions used for
setting-up subcommand parsers had been registred correctly via
decorator.
- Remove old tests that got replaced as part of this paramtrization.

Noticket: Deduplicate testing of command availaibility and help flags:

- Updated CLI tests related to testing of what commands are available,
and if they accept the help (long and short form) flag.
- Commands are provided via Pytest parametrisation.
- Changed tests cover primarily the parser behaviour.

Noticket: Deduplicate testing of CLI invocation:

- Updated CLI tests related to testing of acceptable/expected
invocations.
- Introduced mechanism for specifying CLI invocation that should not
produce errors using Pytest parametirsation.
- Replaced all tests that verify just the parser handling of input
arguments (presence, not necessarily content).

GC-18: Added option for generating a new private key during certificate renewal:

- Implemented functional test for the new scenario.
- Fixed incorrect check for client certificate validity in existing
functional test for client certificate renewal.
- Updated documentation to include information about generating a new
private key during certificate renewal.
- Added option of generating a new private key to the renewal command.
- Updated existing code to use new signature for renewal command and
function.
- Added inline function documentation for the renew command code.
- Implemented relevant unti tests that cover new option.

GC-18: Error-out in case renew is called on uninitialised hierarchy:

- Added functional test for scenario.
- Implemented dummy renew command that for now just verifies the
hierarchy has been initialised.
- Implemented unit tests.

GC-18: Added initial dummy implementation of the renew command:

- Added functional test covering testing of available help for the
renew command.
- Implemented unit tests
- Registered a renew command parser setup function with CLI.

GC-19: Added option for updating server certificate DNS names:

- Added functional test covering the new scenario.
- Added option to server command for updating DNS names for already
issued certificate. Private key is kept for this purpose.
- Implemented unit tests.
- Fixed functional test related to viewing short usage instructions.

GC-16: Implemented issuance of client certificates:

- Added functional test covering basic issuance of client
certificates.
- Replaced the dummy command implementation.
- Added new crypto function that can be used for issuing TLS client
certificates.
- Implemented relevant unit tests.

GC-16: Implemented scenario for issuing client certificates when hierarchy is not initialised:

- Added functional test that checks if an error is shown to user in
case the hierarchy hasn't been initialised prior to issuing a client
certificate.
- Added initial dummy client command implementation.

GC-16: Added client command parser:

- Added functional test for checking availability of client command
and its help.
- Added initial dummy implementation with parser.

GC-17: Removed redundant tests, cleaned-up tests for commands module and fixed wrong directory used for outputting server artifacts in server command:

- Removed CLI tests that check if command errors-out in case the
hierarchy has already been initialised (for init command) or has not
been initialised (for server command). These are part of commands
module tests already.
- Removed unnecessary changing of directory within the commands
tests.
- Fixed issue where server artifacts paths are not calculated
correctly when writing them out (parent directory was not part of
path).

GC-17: Deduplicate exits in command wrapper functions:

- Move all calls to exit to the main function.
- Update signature of all wrapper functions to return status code.
- Update a couple of CLI tests to not fail due to systemexit being
thrown (instead of mocking away too much).

GC-17: Refactored calls to help and usage printing functions:

- Introduced distinct help/usage functions in commands module.
- Wrap the help/usage in similar way to existing commands.
- Added unit tests for new commands and their invocation from CLI.

GC-17: Refactored server command to handle output and return exit code:

- Updated server command to return just a status code.
- Updated existing code and tests that call out to the server command
to use correct function signature.
- Moved output from cli module to commands module.
- Updated existing tests for the server command to test for output
being produced in correct streams.

GC-17: Refactored init command to handle output and return exit code:

- Introduced a holder class for command exit codes.
- Moved output for the cli module to commands module.
- Implemented new tests for verifying the command output.
- Updated existing tests for verifying return value of command output.
- Updated existing code and tests to use the new signature for init
command.

GC-15: Prevent server command from overwriting artifacts and clean-up incorrect CLI tests:

- Added functional test for scenario where a server certificate has
already been issued.
- Updated server certificate issuance command not to overwrite the
artifacts.
- Fixed a couple of both server and init tests related to CLI parsing
to not create artifacts unless necessary, and if necessary to create
artifacts in temporary (test) directory. Otherwise intermittent
failures will happen.

GC-15: Implemented functionality for including extra DNS names in server certificates:

- Added functional test covering the new scenario.
- Updated invocations of relevant commands in existing code to pass-in
the list of extra DNS names where appropriate.
- Updated server command and high-level function for issuing server
certificates to accept list of additional DNS subject alternative
names to include in certificate.
- Fixed existing unit tests.
- Added additional unit tests that cover the new function.

GC-15: Implemented functionality for issuing a server certificate:

- Added functional test covering the user scenario.
- Updated CLI implementation to show user message about issued server
artifacts.
- Implemented functionality in the server command.
- Fixed a small typo in docstring for issue_certificate function.
- Implemented high-level crypto function for issuing server
certificates.
- Implemented additional storage functions for reading an entire CA
hierarchy, individual private keys, and individual certificates.
- Implemented the necessary unit tests covering newly implemented
code.

GC-15: Implemented scenario for server certificate issuance where user has not initialised the CA hierarchy:

- Added functional test that tests if correct error is shown to user
in case he/she has not initialised the CA hierarchy.
- Introduced new function to check if storage is initialised.
- Added initial simplified server command implementation.

GC-15: Added server command parser:

- Added functional test for testing new command presence and help.
- Added initial parser implementation.

GC-3: Implement option for specifying CA hierarchy depth during initialisation:

- Minor fix for option checks to make the more reliable (for short
flags).
- Added functional test for initialising a CA hierarchy with custom
depth.
- Added option for specifying the CA hierarchy depth (defaults to 1).
- Updated the init command to accept and process the CA hierarchy
depth option correctly.
- Updated function used for issuing certificates to accept list of
extensions to be added to certificate.
- Updated function used for generating the CA hierarchy to add the CA
basic constraint extension.

GC-3: Added ability to provide custom CA base name to init command:

- Added functional test to cover the new scenario (providing CA base
name).
- Updated init command to accept the CA base name to be used when
constructing the CA subject DN.
- Updated the existing tests to pass-in the CA base name explicitly.
- Updated the CLI code to allow for user to pass-in the CA base name
via option (both short and long form available).

GC-3: Refactored main functionality of the init command into separate function:

- Introduced a new module (commands) where the majority of command
implementation should reside.
- The cli module should now be a thin wrapper around commands, in
charge of processing input system arguments.
- Refactored the tests accordingly.

GC-3: Implemented CA hierarchy initialisation:

- Added functional test for initialising hierarchy on a fresh
directory.
- Implemented the init command.
- Added two new modules for working with storage and crypto.
- Added cryptography (for certificate issuance and crypto) and
python-dateutil (for better handling of certificate validities) as
installation dependencies.
- Added freezegun as test dependency (helps with testing validity
dates).
- Implemented necessary unit tests.

GC-3: Added dummy command for CA initialisation:

- Fixed test for the help command (help output now includes multiple
comands).
- Added dummy/skeleton implementation for init command parser.

GC-11: Added a help subcommand to the tool:

- Updated functional test for checking on the help subcommand as well.
- Implemented the 'help' subcommand.
- Updated required function signature for the subcommand_parser
decorator (functions should return ArgumentParser instance).
- Fixed a typo in inline documentation.
- Updated the test for subcommand_parser decorator to be a more robust
when checking if function registration works.

GC-11: Updated CLI to display simple usage help:

- Added terse description to the CLI.
- Implemented small mechanism for invoking callback functions attached
to parser.
- Fixed some linting issues in setup script.

GC-11: Added intial dummy CLI skeleton implementation:

- Register entry point in the package setup script.
- Implemented a very basic main function as entry point that
constructs an empty argument parser.
- Implemented functional test for testing if the CLI tool gets invoked
correctly after installation.
- Added unit tests for implemented functionality.