* This push request is about handling Traefik ipallowlist to synapse-admin application.

It's my first push request. If I forgot something please let me know. :-)

* Changed position of variable and naming for better expandebility of traefik options

* Remove useless `noqa var-naming` comment and too many blank lines at the end of the file

---------

Co-authored-by: AkDk7 <joerg@pannbacker.email>
Co-authored-by: Slavi Pantaleev <slavi@devture.com>

Most of these files were defining a service, usually toward the end.
These lines have been moved upward.

Some components (mautrix-signal, mautrix-gmessages, etc.) were defining
a service conditionally (only if metrics are exposed, etc). This was
causing issues like these in the Traefik logs:

> level=error msg="service \"matrix-mautrix-twitter\" error: port is missing" providerName=docker container=matrix-mautrix-twitter-..

This may proof useful to someone in the future.

We've had it on `matrix-nginx-proxy` before, but
our initial support for Traefik did not include any of these security
headers.

Previously, we had to run it at a subpath, like `/synapse-admin`.

We can now dedicate a whole domain and the `/` path to it, should we
wish to do so.

Previously, it had to go through matrix-nginx-proxy.
It's exposed to Traefik directly via container labels now.