Use container network address for communication between IRC bridge and homeserver

This means we need to explicitly specify a `media_url` now,
because without it, `url` would be used for building public URLs to
files/images. That doesn't work when `url` is not a public URL.

roles/matrix-bridge-appservice-irc/defaults/main.yml

@@ -8,6 +8,10 @@ matrix_appservice_irc_docker_image_force_pull: "{{ matrix_appservice_irc_docker_
 
 matrix_appservice_irc_base_path: "{{ matrix_base_data_path }}/appservice-irc"
 
+matrix_appservice_irc_homeserver_url: 'http://matrix-synapse:8008'
+matrix_appservice_irc_homeserver_media_url: 'https://{{ matrix_server_fqn_matrix }}'
+matrix_appservice_irc_homeserver_domain: '{{ matrix_domain }}'
+
 # Controls whether the matrix-appservice-discord container exposes its HTTP port (tcp/9999 in the container).
 #
 # Takes an "<ip>:<port>" or "<port>" value (e.g. "127.0.0.1:9999"), or empty string to not expose.
@@ -25,8 +29,9 @@ matrix_appservice_irc_systemd_wanted_services_list: []
 matrix_appservice_irc_configuration_yaml: |
   #jinja2: lstrip_blocks: True
   homeserver:
-    url: "https://{{ matrix_server_fqn_matrix }}"
-    domain: "{{ matrix_domain }}"
+    url: {{ matrix_appservice_irc_homeserver_url }}
+    media_url: {{ matrix_appservice_irc_homeserver_media_url }}
+    domain: {{ matrix_appservice_irc_homeserver_domain }}
     enablePresence: true
 
 matrix_appservice_irc_configuration_extension_yaml: |