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.
This moves the comments from being just in Jinja,
to actually ending up in the generated `labels` file,
which makes inspection of the final result easier.
Also, some new lines were added here and there to make labels
more legible.
The generated file may still include weird new-lines due to
various `if` statements yielding content or not, but that's not so ugly
anymore - now that we have proper start/end sections that are visible in
the final `labels` file.
