This gets us started on adding a Traefik role and hooking Traefik:

- directly to services which support Traefik - we only have a few of
  these right now, but the list will grow

- to matrix-nginx-proxy for most services that integrate with
  matrix-nginx-proxy right now

Traefik usage should be disabled by default for now and nothing should
change for people just yet.

Enabling these experiments requires additional configuration like this:

```yaml
devture_traefik_ssl_email_address: '.....'

matrix_playbook_traefik_role_enabled: true
matrix_playbook_traefik_labels_enabled: true

matrix_ssl_retrieval_method: none

matrix_nginx_proxy_https_enabled: false

matrix_nginx_proxy_container_http_host_bind_port: ''
matrix_nginx_proxy_container_federation_host_bind_port: ''

matrix_nginx_proxy_trust_forwarded_proto: true

matrix_nginx_proxy_x_forwarded_for: '$proxy_add_x_forwarded_for'

matrix_coturn_enabled: false
```

What currently works is:
reverse-proxying for all nginx-proxy based services **except** for the Matrix homeserver
(both Client-Server an Federation traffic for the homeserver don't work yet)

Switching from doing "post-start" loop hacks to running the container
in 3 steps: `create` + potentially connect to additional networks + `start`.
This way, the container would be connected to all its networks even at
the very beginning of its life.

Related to https://docs.docker.com/engine/deprecated/#separator--of---security-opt-flag-on-docker-run

Docker images are released now so this change can now be pushed.

Container image not published yet.

Reverts #2438

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2427

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2427

`metrics_enabled` should only expose the metrics locally, on the
container network, so that a local Prometheus can consume them.

Exposing them publicly should be done via a separate toggle (`metrics_proxying_enabled`).
This is how all other roles work, so this makes these mautrix roles consistent with the rest.

Fixup for 6a31fba346

Related to f165aa5d48

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2424

Use matrix_bot_chatgpt_context for CHATGPT_CONTEXT

matrix_bot_chatgpt_context=thread

This helps large deployments which need to open up thousands of ports
(matrix_coturn_turn_udp_min_port, matrix_coturn_turn_udp_min_port)

On a test VM, opening 1k ports takes 17 seconds for Docker to "publish"
all of these ports (setting up forwarding rules with the firewall, etc),
so service startup and shutdown take a long amount of time.

If host-networking is used, there's no need to open any ports at all
and startup/shutdown can be quick.

Inspired by: https://www.rtcsec.com/article/cve-2020-26262-bypass-of-coturns-access-control-protection/

Part of a security hardening provoked by:
https://www.rtcsec.com/article/cve-2020-26262-bypass-of-coturns-access-control-protection/

Set OPEN_AI to matrix_bot_chatgpt_openai_pro

Add support for OPENAI_PRO for ChatGPT pro subscriptions.