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-186: Reorder the deprecation tasks for xmpp_server role to make the runs reliable:

- Deprecated apt repository really needs to be removed first in case
it has an unresolvable URL (so the backports repository cache update
would trigger correctly).
- Use the file removal for Prosody repository as well to make sure the
file is dropped.

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-181: Drop support for Debian 9 Stretch from the xmpp_server role:

- Switch to using IPs from VirtualBox default allowed host-only
network subnets.
- Drop Stretch-specific workarounds, code, and tests.

MAR-181: Rename the private signing key for Prosody repository:

- New names make a bit more sense, and avoids Emacs trying to decrypt
the file.

MAR-151: Drop rcconf workaround:

- The workaround was needed on Debian Jessie because the systemctl
is-enabled command did not behave correctly for SysV init scripts.
- Drop the installation of the rcconf package.
- Use the "enabled" parameter in service module instead.

MAR-163: Attach noqa directives to task names (if skipping is applicable on task level) for better uniformity:

- This way the indentation of comment describing the directive can
always be on the same level everywhere (irrespective of how the rest
of task arguments are listed).

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-148: Fixing linting errors:

- Do not compare against booleans when value is already boolean in
"when" conditions.
- Use pipefail in conjunction with setting the shell to Bash when
extracting the backup encryption key IDs.
- Do not compare variables to empty strings in "when" conditions. This
change currently works only for complex variables (stuff can break
badly in case of simple variables in current default Ansible
configuration).
- Fix missing space in one of Jinja2 templates.

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

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

MAR-135: Switch to using run_handlers instead of handlers as variable:

- Updated all roles to now depend on run_handlers being set to True in
order to force execution of handlers.

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-114: Updated task syntax for bootstrap, preseed and xmpp roles:

- Updated web_server, php_website, and wsgi_website roles.
- Added and removed quoting where it makes sense.
- Switched to using expanded syntax (instead of one-liners).
- Updated ordering of arguments in task definitions.

MAR-31: Implemented tests and small fixes for xmpp_server role:

- Updated test playbook to deploy simple XMPP non-interactive tool.
- Updated test playbook to include an additional administrator for server
hosting domain2 and domain3.
- Updated test playbook to enable backup on parameters-optional test instance.
- Use expanded syntax for deploying TLS key and certificate in order to prevent
mangling of tab characters.
- Set permissions on deployed Prosody configuration file in order to prevent
LDAP password from being world-readable.
- Implemented tests for backup functionality.
- Implemented tests for client connectivity.
- Implemented a number of tests that ensure XMPP server is deployed correctly.
- Full functionality cannot be tested (like MUC and file proxy) due to partial
lack of CLI-based tools.

MAR-31: Added scaffolding for testing xmpp_server role:

- Fixed wrong default for xmpp_domains parameter (should be a list).
- Added Molecule configuration file with LDAP server, client, and two XMPP
server instances.
- Added test playbook that sets-up all servers.
- Fixed mode syntax issues (use lead zero).
- Added data required for testing.
- Added dummy file with tests.