* Add matrix-registration-bot

This adds an install and uninstall task plus helpers. The bot is disabled by default.
This commit does not include documentation, yet. In short, the bot can be enabled by adding
matrix_bot_matrix_registration_bot_enabled: true
matrix_bot_matrix_registration_bot_matrix_user_password: "verysecret"
matrix_bot_matrix_registration_bot_matrix_admin_token: "supersecret"
to the host_vars

* Change bot username to bot.matrix-registration-bot following convention

* Address smaller remarks, fix local docker build

* Switch to an env file

* Add environment variables extension for additional config

* Add documentation for the matrix-registration-bot

* Add screenshot on how to obtain admin access token

* Use bot as admin to only have one access token (bot and admin api)

* Use cleaner setting of matrix_synapse_registration_requires_token

* Use config file for cleaner more secure usage

* Delete unneeded env

* Rename vars to make usage clear

* Fix typos/wording and add notice about logging out

* Convert configuration to use |to_json

* Reorder role includes

Nothing should be after `matrix-common-after`.

`matrix-bot-matrix-registration-bot` can probably be anywhere, but it makes sense to put it next to the other `matrix-bot-*` roles.

* Minor group_vars/matrix_servers touchups

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* add borg backup

* lint fix

* add exlclude patterns

* missed in the #1726 fix for honoroit

* feedback

* Fix indentation

* feedback

* feedback

* feedback

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

* Copy/update mautrix_facebook group_vars to mautrix_twitter
* Replace facebook -> twitter, fb -> twt, remove presence var
* Enable playbook in setup.yml

This commit introduces a new role that downloads and installs the
prometheus community postgres exporter  https://github.com/prometheus-community/postgres_exporter.
A new credential is added to matrix_postgres_additional_databases that
allows the exporter access to the database to gather statistics.
A new dashboard was added to the grafana role, with some refactoring
to enable the dashboard only if the new role is enabled.
I've included some basic instructions for how to enable the role in
the Docs section.

In terms of testing, I've tested enabling the role, and disabling
it to make sure it cleans up the container and systemd role.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/683

Also includes the dashboards for Synapse and for Node Exporter.

Again has only been tested on debian amd64 so far, but the grafana docker image is available for arm64 and arm32. Nice.

Basic system stats, to show stuff the synapse metrics
can't show such as resource usage by bridges, etc

Seems to work fine as well.

This too has only been tested on debian amd64 so far

Initial attempt. Seems to work fine.

Only tested on debian amd64 so far

If we load it at runtime, during matrix-synapse role execution,
it's good enough for matrix-synapse and all roles after that,
but.. it breaks when someone uses `--tags=setup-nginx-proxy` alone.

The downside of including this vars file like this in `setup.yml`
is that the variables contained in it cannot be overriden by the user
(in their inventory's `vars.yml`).
... but it's not like overriding these variables was possible anyway
when including them at runtime.

Fixes #562 (Github Issue)