Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2524

We don't need this anymore. No one should be using matrix-nginx-proxy
anymore.

Change documentation for host bind port when fronting traefik with another reverse proxy

own traefik server option must have the path to the acme.json. Otherwise the service will not start.

Otherwise the public hookshot url will use http and not https

The newly extracted role also has native Traefik support,
so we no longer need to rely on `matrix-nginx-proxy` for
reverse-proxying to Ntfy.

The new role uses port `80` inside the container (not `8080`, like
before), because that's the default assumption of the officially
published container image. Using a custom port (like `8080`), means the
default healthcheck command (which hardcodes port `80`) doesn't work.
Instead of fiddling to override the healthcheck command, we've decided
to stick to the default port instead. This only affects the
inside-the-container port, not any external ports.

The new role also supports adding the network ranges of the container's
multiple additional networks as "exempt hosts". Previously, only one
network's address range was added to "exempt hosts".

This also updates `docs/configuring-playbook-own-webserver.md`,
trying to make it up-to-date with all recent changes.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2375

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2451

Check for empty string instead of Null to verify if an openid_server_name is pinned.

This is an advanced feature with dubious usefulness.
Putting it in the default config just confuses people.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2220