Add support for more flexible container port exposing

Fixes #171 (Github Issue).

roles/matrix-bridge-appservice-irc/tasks/validate_config.yml

@@ -14,3 +14,11 @@
       You need to define additional configuration in `matrix_appservice_irc_configuration_extension_yaml` or to override `matrix_appservice_irc_configuration`.
   when: "matrix_appservice_irc_configuration.ircService|default(none) is none"
 
+- name: (Deprecation) Catch and report renamed appservice-irc variables
+  fail:
+    msg: >-
+      Your configuration contains a variable, which now has a different name.
+      Please change your configuration to rename the variable (`{{ item.old }}` -> `{{ item.new }}`).
+  when: "item.old in vars"
+  with_items:
+    - {'old': 'matrix_appservice_irc_container_expose_client_server_api_port', 'new': '<superseded by matrix_appservice_irc_container_http_host_bind_port>'}