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

- Roll-out LDAP client configuration since Bullseye does not come with
a stock one at /etc/ldap/ldap.conf that sets the trust anchor
correctly for validating LDAP server certificates.
- Drop the backports pinning in case of Bullseye (for now let's try to
keep the Buster and Bullseye at same versions for simplicity).
- Drop installation of Python apt bindings (no longer used).
- Tests for Buster and Bullseye need to be split-up a bit due to some
differences around backports etc.

MAR-189: Dropped deprecation-related tasks and tests for xmpp_server role:

- Migration from Prosody project repositories should have been done
already as part of the 7.0.1 release.
- Simplifies the code a bit.
- Drop leftover deprecated library plugin path.

MAR-181: Refactor the Prosody package version checks:

- Move the Prosody package version check into default set of tests.

MAR-181: Deploy Prosody modules (in order to use the LDAP authentcation):

- Replaces the rolled-out-by-hand authentication module, making it
less dependent on upstream repository.

MAR-181: Install Prosody from Debian backports repository:

- This way we should be able to get way more features available, and
reduce chances of breaking upgrades from upstream project towards
Debian-provided packages due to eventual bigger differences between
the nightly builds and official releases.

MAR-181: Use Debian-provided Prosody package instead of project repository:

- Upstream repository has a tendency to drop support for older Debian
releases, and to completely wipe old version repositories.
- It should be way less hassle to simply start using the
Debian-provided packages instead.
- Introduces deprecation tests to check if the role will also clean-up
the non-Debian packages.

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

- Updated role reference documentaiton.
- Updated role meta information.
- Updated tests.
- Enable lower-level TLS protocols (1.0/1.1) in global OpenSSL
configuration file on Buster in order to be able to test the
xmpp_server_tls_protocol parameter (otherwise Prosody completely
refuses to use them even if listed in its configuration).
- Move stretch-specific tests into its own file (for backported
lua-ldap library), and run them on Debian 9 Stretch machines only.

MAR-174: Enable Message Carbons (XEP-0280) and Message Archive Management (XEP-0313) via xmpp_server role:

- Updated release notes.
- Updated role reference documentation.
- Enable the two modules via Prosody configuration file, and set the
archive expiration configuration option for Prosody.
- Updated tests.

MAR-164: Fix Prosody TLS configuration in xmpp_server role:

- Added warning to role reference documentation about what DNS names
need to be included in the subject alternative name of issued
certificate used for Prosody.
- Added crontab with script that validates the certificate on daily
basis.
- Updated tests to include the proxy.DOMAIN and conference.DOMAIN DNS
names in subject alternative name for generated test certificates.
- Added and updated tests that cover new functionality.
- Fixed the Prosody TLS configuration to have common parameters
specified in general section, and any kind of overrides (mainly the
ciphers) in more specific sections.
- Updated release notes.

MAR-173: Switch to using Prosody 0.11 as default version in the xmpp_server role:

- Updated default value for the Prosody package parameters.
- Configure the backports repository on the server, and pin the
lua-ldap package to be installed from the backports
repository (needed for Lua 5.2 support).
- Drop the explicit installation of lua-sec library - it is already
installed as pre-requisite for the Prosody package.

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

MAR-162: Make the xmpp_tls_certificate and xmpp_tls_key parameters mandatory in xmpp_server role:

- Dropped the defaults from wsgi_server role.
- Updated group variables in role tests.
- Changed the key/certificate file extensions to be more descriptive.
- Updated role reference documentation.
- Updated usage instructions to include the mandatory parameters.
- Deduplicated tests for the TLS files.

MAR-149: Switch to using File.content_string instead of File.content in tests for all roles:

- The .content variant returns contents as bytes, while the
content_string returns a string (which is what is wanted in
practically all cases).

MAR-138: Switch to using Prosody stable branch nightlies:

- Introduced additional parameter for specifying name of Prosody
package to install.
- Updated tests.

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

- Updated tests to include Debian 9 in testing. Existing private keys
are reused where possible (since most of the naming is identical
between the machines with jessie/stretch).
- Updated invocation of sendxmpp in tests as workaround for
https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=854210.
- Updated testing of imported keys to accomodate differences between
gpg/gpg2 (used by apt-key in Jessie/Stretch).

MAR-129: Updated xmpp_server role for Ansible 2.5.x and new Molecule:

- Include top-level lint configuration in test configuration.
- Fixed linting errors.
- Moved test playbook variables into group_vars and host_vars.
- Fixed deprecation warnings from Ansible.
- Updated how hosts are referenced within tests.

MAR-128: Upgraded tests for xmpp_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.
- Renamed hosts to include the Debian version.
- Updated names for some of the test data to cater to change in host
names.
- Switched to using more robust task for populating /etc/hosts.