GC-45: Update copyright information:

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

GC-45: Use non-naive datetime objects that include timezone:

- Newer versions of cryptography prefer/insists on use of UTC-based
datetime objects with correctly set timezone.

GC-45: Replace freezegun with time-machine for data/time-related tests:

- The freezegun is no longer maintained, and it also does not handle
timezones that well.
- The time-machine project seems to be actively maintained, and
provides the same functionality.

GC-37: Use KeyGenerator instead of generate_private_key in unit tests:

- Replaced all uses of generate_private_key with KeyGenerator
invocations that explicitly request 2048-bit RSA.

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: 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-26: Fix wrong issuer DN in client and server certificates:

- Updated tests to generate deeper hierarchy so the issue is more
likely to be triggered.
- Applied necessary fixes (a simple switch to using subject instead of
issuer from the issuer certificate - which should be quite obvious).

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-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: Added functional renew command implementation:

- Added functional test covering the use of renew command for server
and client certificates.
- Added new crypto function for renewing a certificate based on
existing certificate, issuer private key, and issuer certificate.
- Fixed use of incorrect output stream in one of the existing tests
for the renew command.
- Added unit tests covering new functionality.

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-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-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: 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.