Automatically enable openid listeners when ma1sd enabled

ma1sd requires the openid endpoints for certain functionality.
Example: 90b2b5301c/src/main/java/io/kamax/mxisd/auth/AccountManager.java (L67-L99)

If federation is disabled, we still need to expose these openid APIs on the
federation port.

Previously, we were doing similar magic for Dimension.
As per its documentation, when running unfederated, one is to enable
the openid listener as well. As per their recommendation, people
are advised to do enable it on the Client-Server API port
and use the `federationUrl` variable to override where the federation
port is (making federation requests go to the Client-Server API).

Because ma1sd always uses the federation port (unless you do some
DNS overwriting magic using its configuration -- which we'd rather not
do), it's better if we just default to putting the `openid` listener
where it belongs - on the federation port.

With this commit, we retain the "automatically enable openid APIs" thing
we've been doing for Dimension, but move it to the federation port instead.
We also now do the same thing when ma1sd is enabled.

docs/configuring-playbook-federation.md

@@ -37,3 +37,13 @@ matrix_synapse_federation_enabled: false
 ```
 
 With that, your server's users will only be able to talk among themselves, but not to anyone who is on another server.
+
+**Disabling federation does not necessarily disable the federation port** (`8448`). Services like [Dimension](configuring-playbook-dimension.md) and [ma1sd](configuring-playbook-ma1sd.md) normally rely on `openid` APIs exposed on that port. Even if you disable federation and only if necessary, we may still be exposing the federation port and serving the `openid` APIs there. To override this and completely disable Synapse's federation port use:
+
+```yaml
+# This stops the federation port on the Synapse side (normally `matrix-synapse:8048` on the container network).
+matrix_synapse_federation_port_enabled: false
+
+# This removes the `8448` virtual host from the matrix-nginx-proxy reverse-proxy server.
+matrix_nginx_proxy_proxy_matrix_federation_api_enabled: false
+```