nagios-plugins-contrib not available on bullseye

Improved automatic settings for ssh agent.

Load and mem services against `physical` machine and not lxc guest.

So that ssh-agent Host can be actively monitored by the Icinga controller.

Add role prefix to role specifig variable to avoid conflicts when
using multiples role on the same machine on the same play.

(IcingaWeb2) Move configuration (user preferences) backend from INI
files to a dedicated pgSQL db.

- (Icinga2) Preseed correctly all the debconf variables to have IDO db created
  and populated by `icinga2-ido-pgsql` deb installation script.

- (IcingaWeb2) Use a different user, `www-data`, with lower
  privileges, to access the IDO db in read-only mode.

- Use everywhere socket (local ident) authentication to PostgreSQL to
  avoid local service password.

(IcingaWeb2) Configuration issues fixed:

- Missing `php-fpm` requirement.

- Migrating php7.0 -> php 7.3 in nginx config location config file.

- Fixed `rewrite` rule in nginx configuration:
    When usign `/icingaweb2` as rewrite target nginx automatically
    expand the redirect 302 response as
    `$scheme://$remote_host:$remote_port/icingaweb2`, causing
    connection to fail when behind a *reverse proxy*, because
    remote_post and remote_host are incorrect.

- Remove hardcoded `status.lilik.it` in `meta/main.yaml`,
  `server_fqdn` is already defined in `defaults/main.yaml` as
  `{{ ansible_hostname }}.{{ domain }}`.

(IcingaWeb2) LDAP:

- procedure to automatically issue service credetinals to authenticate
  with the ldap server.

- starttls secured ldap connection with service account.

- use of the variable `base_dn` instead of hard-coded values in config
  files.

(IcingaWeb2) CONFIGURATION:

- fixed rsync parameters.

- resource renaming.

- remove the handling of which template to use
- do not access parent role
- update riot-web nginx configuration
- update icinga role to use new nginx templating
- update synapse nginx configuration
- update matrix role to use new nginx templates
- update dokuwiki to use new nginx template
- extend nginx template in dokuwiki
- update login role to new nginx templates
- add protocol for default option
- add extra block to nginx template
- update riote-web version
- fix template extension for riot web nginx definition
- update login template for nginx endpoint