Initial work on matrix-homeserver-proxy role and eliminating matrix-nginx-proxy

This is still very far from usable.

Various bridges and bots are still talking to
`matrix-nginx-proxy` instead of the new `matrix-homeserver-proxy` role.
These services need to be reworked. While reworking them,
various cleanups are being done as well as adding Traefik-labels to
those that need them.

roles/custom/matrix-bot-postmoogle/tasks/validate_config.yml

@@ -7,4 +7,6 @@
   when: "item.when | bool and vars[item.name] == ''"
   with_items:
     - {'name': 'matrix_bot_postmoogle_password', when: true}
+    - {'name': 'matrix_bot_postmoogle_container_network', when: true}
+    - {'name': 'matrix_bot_postmoogle_homeserver', when: true}
     - {'name': 'matrix_bot_postmoogle_database_hostname', when: "{{ matrix_bot_postmoogle_database_engine == 'postgres' }}"}