This change adds a section that lets the reader know that it is possible to enable synapse metrics and references the relevant documentation.

It aims to be short and concise, leaving the specifics to the referenced documentation, while still giving the reader a good idea of what it is and what it is for.

Similar to:
362954aeab

This warning was added because of:
https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2090

The problem has since been fixed by:
e9e84341a9

This current patch was provoked by:
https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2352

* one var to control encryption across all bridges

* move var to matrix-base

The playbook auto-generates these passwords, so there's no need
to ask people to do it manually.

See #2529

It's not strictly required yet, but certain versions of Ansible display warnings
if passlib is missing. The non-passlib crypto usage is deprecated, so
passlib will become a requirement in newer Ansible versions. It's only a
matter of time.

* fixes #2586

For backward-compatibility reasons, this playbook uses `matrix` as its
main and default database.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2515

The variable was necessary when multiple playbooks could have
potentially tried to manage a shared `devture-traefik.serivce` systemd service
and shared `/devture-traefik` directory.

Since adcc6d9723086f65f1a72, we use our own `/matrix/traefik`
(`matrix-traefik.service`) installation and no conflicts can arise.
It's safe to always enable the role, just like we do with all the other roles.

Completely untested.

This new role also adds native Traefik support and support for other
(non-`amd64`) architectures via self-building.

The new version includes the `passlib` Python module.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2532

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2524

We don't need this anymore. No one should be using matrix-nginx-proxy
anymore.

Change documentation for host bind port when fronting traefik with another reverse proxy

own traefik server option must have the path to the acme.json. Otherwise the service will not start.