Dendrite uses a lot of databases, but a single (`dendrite`) role, which
leads to `matrix_postgres_import_roles_to_ignore` being something like
`['dendrite', 'dendrite', 'dendrite', ...]` needlessly.

This leads to weird regexes being generated for
`matrix_postgres_import_roles_ignore_regex`.
It's not that it hurts, but it just looks odd.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2211

We haven't encountered such a problem yet, but it doesn't hurt to
make things more robust.

These values that we were setting also make sense in the context of the
`matrix-postgres` role even when not used within the playbook.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2180

Just specifying `15` means we won't automatically re-pull `15.1` when it comes out.

We're overriding these in the correct way in `group_vars/matrix_servers`
so this wasn't causing any problem in practice.

This mostly fixes `key-order` warnings around
`block` statements.

Reference: https://ansible-lint.readthedocs.io/en/latest/default_rules/#var-spacing

CVE: https://security-tracker.debian.org/tracker/CVE-2022-1552
Source: https://www.postgresql.org/about/news/postgresql-143-137-1211-1116-and-1021-released-2449/
Postgres 9.6 upgrade (**not a CVE fix, 9.x still vulnerable**): https://www.postgresql.org/docs/release/9.6.24/

Related to:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1682
- https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1679

In short, the problem is that older Postgres versions store passwords
hashed as md5. When you dump such a database, the dump naturally also
contains md5-hashed passwords.
Restoring from that dump used to create users and updates their passwords
with these md5 hashes.
However, Postgres v14 prefers does not like md5-hashed passwords now (by default),
which breaks connectivity. Postgres v14 prefers `scram-sha-256` for
authentication.

Our solution is to just ignore setting passwords (`ALTER ROLE ..`
statements) when restoring dumps. We don't need to set passwords as
defined in the dump anyway, because the playbook creates users
and manages their passwords by itself.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/1340

Signed-off-by: Ahmad Haghighi <haghighi@fedoraproject.org>

In short, this makes Synapse a 2nd class citizen,
preparing for a future where it's just one-of-many homeserver software
options.

We also no longer have a default Postgres superuser password,
which improves security.

The changelog explains more as to why this was done
and how to proceed from here.

We were running into conflicts, because having initialized
the roles (users) and databases, trying to import leads to
errors (role XXX already exists, etc.).

We were previously ignoring the Synapse database (`homeserver`)
when upgrading/importing, because that one gets created by default
whenever the container starts.

For our additional databases, it's a similar situation now.
It's not created by default as soon as Postgres starts with an empty
database, but rather we create it as part of running the playbook.

So we either need to skip those role/database creation statements
while upgrading/importing, or to avoid creating the additional database
and rely on the import for that. I've gone for the former, because
it's already similar to what we were doing and it's simpler
(it lets `setup_postgres.yml` be the same in all scenarios).

This can be used by various bridges, etc., to import an SQLite
(or some other supported) database into Postgres.

Being more explicit sounds better.

We'll most likely use one that matches the database name, but
it's better to have it configurable.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/746

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/727

This is both for consistency with 93cc71cb69976c
and for making things more obvious.