Added a role for the bridge mautrix-signal

We try to only use console logging (going to journald) for everything,
instead of logging things twice (or more).

While it's kind of nice having it, it's also somewhat raw
and unnecessary.

Having a good default and not even mentioning it seems better
for most users.

People who need a more exposed bridge (rare) can use
override the default configuration using
`matrix_mautrix_signal_configuration_extension_yaml`.

The answer to these is: it's good to have them in both places.
The role defines the obvious things it depends on (not knowing
what setup it will find itself into), and then
`group_vars/matrix_servers` "extends" it based on everything else it
knows (the homeserver being Synapse, whether or not the internal
Postgres server is being used, etc.)

We used to store them in data/, but that seems inappropriate,
since it's just static configuration that the playbook can recreate.

Keeps up with a1f64f5159 (diff-0ccf69eb4d59a7645eb4d0a0b077e693948edb33ad06df043bba3fb30122879b)

Example Files for Caddy2

Check for buggy version of Ansible that Ubuntu 20.04 provides

We need to suppress systemd service-stopping requests in certain rare
cases like https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/771

That issue seems to describe a case, where a migration from mxisd to
ma1sd was happening (DB files had just been moved), and then we were
attemping to stop `matrix-ma1sd.service` so we could import that database into
Postgres. However, there's neither `matrix-mxisd.service`, nor
`matrix-ma1sd.service` after `migrate_mxisd.yml` had just run, so
stopping `matrix-ma1sd.service` was failing.

We've had people who get the impression that well-known = bad,
DNS SRV = good, and who try to use DNS SRV for server delegation.

While it's true that DNS SRV can be superior for high-availability
scenarios, it's much harder to set up and comes with its own potential
downsides.

Using the well-known method is more straightforward and is enough
for almost all of us. Throwing people into the deep for no good
reason is not nice. Hopefully wording is better after this patch.

Merge

Fix concatenation of additional databases

Otherwise the postgres upgrade fails with the following error:

Unexpected templating type error occurred on ({{
  [matrix_postgres_connection_username]
  +
  matrix_postgres_additional_databases|map(attribute='username')
}}
): can only concatenate list (not "generator") to list

Fixes a problem like this:
> File "/usr/lib/python3.8/site-packages/mautrix/bridge/e2ee.py", line 79, in __init__
> raise RuntimeError("Unsupported database scheme")

mautrix-python's e2ee.py module expects to find `postgres://` instead of
`postgresql://`.

This is 8b6174786b done right. There were many more fields
that we had to account for.

Use role relative paths for references to matrix-postgres role

This makes the `sqlite://` URI match what we were using before
and what the config expects.

Some Ansible installations choke on it, it seems.
Similar to 9f00970c90

Update updating-users-passwords.md

We've hit this problem before as well. Certain Ansible installations
choke on it.

Fixed markdown error

Related to
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/740
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/686

postgres: create databases for all services