MAR-192: Allocate a bit more memory to LDAP server helper for mail_server tests:

- Debian 12 Bookworm is a bit more memory-hungry.

MAR-192: Added support for Debian 12 Bookworm to mail_server role:

- Allow use of older versions of TLS on Bookworm for testing of
related optional parameters.
- Install the IMAP CLI testing tool under its own virtual environment
in order to avoid warnings and errors when trying to install it
globally under Debian 12 Bookworm.
- Update the lists of expected TLS protocols and ciphers.

MAR-189: Disable use of KVM paravirtualisation provider with Vagrant/VirtualBox:

- The VMs seem to randomly hang when the (KVM) clock source gets
initialised right after getting past the bootloader. Helps run the
tests in a way more reliable way.
- Should be removed if upgrading to latest kernel/VirtualBox versions
helps.

MAR-189: Added support for Debian 11 Bullseye to mail_server role:

- Shorten the backup client username so it would be under 32
characters.
- Switch all helper VMs to using the Debian 11 Bullseye as well.
- Drop the architecture suffix from hostnames.
- Update the hostname for client VMs.
- Fix the incorrect format for the message ID used in various mail
delivery tests.

MAR-183: Use local caching and serving of ClamAV database files:

- Helps avoid getting stuck due to hitting the upstream rate limiting,
and also speeds-up the database downloads.

MAR-181: Increase memory for mail_server role test machines:

- ClamAV eats-up quite a bit of memory, and 1536MB is not enough. Most
likely the memory usage will grow over time as the anti-virus
database grows since it is loaded up into memory.

MAR-181: Drop support for Debian 9 Stretch from mail_server role:

- Switch to using IPs from VirtualBox default allowed host-only
network subnets.
- Use Debian Buster for helper machines.
- Drop Stretch-specific code and tests.

MAR-151: Added support for Debian 10 Buster to mail_server role:

- Updated role reference documentaiton.
- Updated role meta information.
- Updated tests.
- Improve handling of configured IP in tests to avoid hard-coding the
value in the relevant test for Postfix configuration file content.

MAR-175: Mail server should be opportunistic in using TLS when delivering mail to remove servers:

- Previously the mail server would only deliver mails over plaintext.
- Deploy a simple SMTP server on both client1/client2
machines. Servers are set-up to require/refuse the STARTTLS over
SMTP.
- Added tests for checking if STARTTLS is used when available for mail
delivery.
- Fixed the wrong configurtion (making sure the TLS security level is
properly set for Postfix).

MAR-150: Use fixtures for X.509 artefacts in the mail_server role:

- Removed the statically generated artefacts.
- Generate X.509 artefacts for tests using Gimmecert.
- Updated paths to point to generated artefacts.
- Introduced cleanup playbook for removing generated artefacts.
- Increase allocated RAM for the mail server to avoid OOM and
swapping.

Noticket: Improve reliability for mail_server tests, detection of running ClamAV daemon:

The fixes mainly help with reliability of tests against the
mail_server role due to ClamAV not becoming available before the tests
get run. This normally is not a real issue in production (since the
daemon will become available farily quickly).

Changes made:

- Wait for ClamAV socket to become available in mail_server
role (otherwise mail delivery failures can happen).
- Increase memory used in mail server instances for testing to avoid
OOM killer kicking-in during tests.
- Introduce slight delay when running local alias tests to avoid race
condition.
- Formating fix in task that waits for ClamAV database to be
available.

MAR-148: Disable Ansible's default of enforcing group names without dashes through Molecule configuration files:

The following links might be a useful read:

- https://github.com/ansible/ansible/issues/56930 (issues relaetd to
lack of docs, but many complaints and explanations within)
- https://groups.google.com/forum/#!topic/ansible-devel/bjAcM9ferIw

MAR-132: Added support for Debian 9 (Stretch) to mail_server role:

- Updated Molecule configuration to include set-up of additional
instances for testing.
- Updated configuration for test instances.
- Use separate clients in testing of Jessie/Stretch instances.
- Duplicate private keys/certificates for testing of mandatory
parameters on Debian 9.
- Refactored testing of mail deliveries (via swaks) to use
test-generated message ID - improves reliability and solves some
incompatibilities between swaks version in Jessie and Stretch.
- Updated tests for TLS testing to take into account newer OpenSSL
error/output messages. A bit of an ugly hack at the moment, but
beats duplicating tests for now.

MAR-129: Updated mail_server role for new Molecule and Ansible:

- Moved variables from test playbooks into group/host vars.
- Fixed linting errors.
- Reference custom top-level linting configuration file in tests.
- Fixed deprecation errors reported by Ansible.
- Updated how the hosts on which the tests should be run are
referenced.

MAR-128: Upgraded tests for mail_server role:

- Switch to new Molecule configuration.
- Updated set-up playbook to use become: yes.
- Moved some preparatory steps outside of the main playbook (eases
idempotence tests).
- Updated tests to reference the yml inventory file.
- Updated tests to use new fixture (host instead of individual ones).
- Switched to extracting hostname instead of hard-coding it in a
couple of tests.
- Fixed some linting issues.
- Renamed the hosts to make it easier to extend in future.
- Renamed some data files to ensure they correspond correctly to new
hostnames.
- Rewrote logic behind setting-up the /etc/hosts a bit, and expanded
the names to include the new hostnames.
- Updated a couple of tests to correspond to correct filenames (that
have been renamed).
- Updated a couple of tests to address the new server naming.
- Set explicitly the backup client username to avoid 32-charactr
limitation on Linux usernames.