Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2918

Related to https://github.com/matrix-org/synapse/pull/15488

Many of these do depend on the Synapse master process (`matrix-synapse.service`),
so it makes sense to do it.

Furthermore, we're doing it so that one can stop the `matrix-synapse.service`
service and have systemd cascade this into stopping all the workers as well.

This is useful for easily stopping all of Synapse, so that Postgres
upgrades (`--tags=upgrade-postgres`) can happen cleanly.
Postgres upgrades currently stop `devture_postgres_systemd_services_to_stop_for_maintenance_list` which
includes Synapse, but stopping just the master process and leaving workers running is not safe enough and sometimes leads to errors like:

> ERROR:  insert or update on table "event_forward_extremities" violates foreign key constraint "event_forward_extremities_event_id"

With this dependency in place, stopping `matrix-synapse.service` will stop all Synapse processes.

Related to https://github.com/matrix-org/synapse/pull/16265

Signed-off-by: saces <saces@c-base.org>

Signed-off-by: saces <saces@c-base.org>

Hopefully fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2849

Related to:
- https://github.com/matrix-org/synapse/issues/16101
- https://github.com/matrix-org/synapse/issues/16208

matrix-synapse/tasks/setup_uninstall.yml would previously not run unless
Synapse was completely disabled.

`spam_checker` has been deprecated for quite a while.
While it still probably works and while newer versions of
mjolnir-antispam still use it, we should switch to the new API.

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

Related to:
- e4f545c452
- 2481b7dfa4

We've prepared for this by adding the `main` process to the `instance_map` a long time ago,
in 49cb8b7b11.

Related to 0f02f0b4da

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

Now that Element v1.11.32 is out and https://github.com/vector-im/element-web/issues/19605 is fixed
(by https://github.com/matrix-org/matrix-react-sdk/pull/10975), we don't
need to force-disable this login type.

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

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

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

Related to:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2698
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2700

This was mostly affecting the stream writer (events) worker, which was
being reported as unhealthy. It wasn't causing any issues, but it just
looked odd and was confusing people.

As an alternative to hitting the regular `/health` healthcheck route (on
the "client" API which this stream writer does not expose),
we may have went for hitting some "replication" API endpoint instead.

This is more complicated and likely unnecessary.