Related to:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3337
- https://github.com/geerlingguy/ansible-role-docker/pull/436

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3307

We may have had another migration task before, but I cannot find it now.

Some people have reported a leftover systemd timer and service,
so it's evident that not everyone has gone through that previous migration.

This changes the behavior of
`matrix_playbook_migration_matrix_nginx_proxy_uninstallation_enabled`
and is against what we initially described in the changelog entry,
but I've discovered some problems when the `matrix-nginx-proxy` service
and container remain running. They need to go.

After some checking, it seems like there's `/_synapse/client/oidc`,
but no such thing as `/_synapse/oidc`.

I'm not sure why we've been reverse-proxying these paths for so long
(even in as far back as the `matrix-nginx-proxy` days), but it's time we
put a stop to it.

The OIDC docs have been simplified. There's no need to ask people to
expose the useless `/_synapse/oidc` endpoint. OIDC requires
`/_synapse/client/oidc` and `/_synapse/client` is exposed by default
already.

Seems like calling these tasks got removed at some point
while merge the `bye-bye-nginx-proxy` branch.

Auto-enabling the OIDC APIs is convenient for people
using the new `matrix_synapse_oidc_*` variables.

We'd be adding integration with an internal Traefik entrypoint
(`matrix_playbook_internal_matrix_client_api_traefik_entrypoint`),
so renaming helps disambiguate things.

There's no need for deperecation tasks, because the old names
have only been part of this `bye-bye-nginx-proxy` branch and not used by
anyone publicly.

This also adds labels for Synapse. Support for other homeservers and
components will be added later.

This requires at least `v0.14.0-2` of the `prometheus-postgres-exporter`
Ansible role.

This requires at least `v1.7.0-2` of the `prometheus-node-exporter`
Ansible role.

This also updates validation tasks and documentation, pointing to
variables in the matrix-synapse role which don't currently exist yet
(e.g. `matrix_synapse_container_labels_client_synapse_admin_api_enabled`).

These variables will be added soon, as Traefik labels are added to the
`matrix-synapse` role. At that point, the `matrix-synapse-reverse-proxy-companion` role
will be updated to also use them.

matrix-nginx-proxy is going away and this is one of the features it
offered.

This feature will have no equivalent in our new Traefik-only
setup, although it's possible to implement it manually by using
`matrix_client_element_container_labels_additional_labels`

This is still very far from usable.

Various bridges and bots are still talking to
`matrix-nginx-proxy` instead of the new `matrix-homeserver-proxy` role.
These services need to be reworked. While reworking them,
various cleanups are being done as well as adding Traefik-labels to
those that need them.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2999
Related to https://github.com/geerlingguy/ansible-role-docker/pull/410

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.