appservice: add and use homeserver_container_* vars (#2045)

* appservice: add and use matrix_homeserver_* vars

* appservice: use the new vars

* Apply suggestions from code review

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

roles/matrix-dendrite/defaults/main.yml

@@ -43,8 +43,19 @@ matrix_dendrite_container_http_host_bind_address: ""
 matrix_dendrite_container_https_host_bind_address: ""
 
 # A list of extra arguments to pass to the container (`docker run` command)
+# Also see `matrix_dendrite_container_arguments`
 matrix_dendrite_container_extra_arguments: []
 
+# matrix_dendrite_container_runtime_injected_arguments is a list of extra arguments to pass to the container.
+# This list is built during runtime. You're not meant to override this variable.
+# If you'd like to inject your own arguments, see `matrix_dendrite_container_extra_arguments`.
+matrix_dendrite_container_runtime_injected_arguments: []
+
+# matrix_dendrite_container_arguments holds the final list of extra arguments to pass to the container.
+# You're not meant to override this variable.
+# If you'd like to inject your own arguments, see `matrix_dendrite_container_extra_arguments`.
+matrix_dendrite_container_arguments: "{{ matrix_dendrite_container_extra_arguments + matrix_dendrite_container_runtime_injected_arguments }}"
+
 # A list of extra arguments to pass to the container process (`dendrite-monolith` command)
 # Example:
 # matrix_dendrite_process_extra_arguments:
@@ -104,8 +115,19 @@ matrix_dendrite_container_additional_volumes: []
 # A list of appservice config files (in-container filesystem paths).
 # This list gets populated dynamically based on Dendrite extensions that have been enabled.
 # You may wish to use this together with `matrix_dendrite_container_additional_volumes` or `matrix_dendrite_container_extra_arguments`.
+# Also see `matrix_dendrite_app_service_config_files_final`
 matrix_dendrite_app_service_config_files: []
 
+# matrix_dendrite_app_service_runtime_injected_config_files is a list of appservice config files.
+# This list is built during runtime. You're not meant to override this variable.
+# If you'd like to inject your own arguments, see `matrix_dendrite_app_service_config_files`.
+matrix_dendrite_app_service_runtime_injected_config_files: []
+
+# matrix_dendrite_app_service_config_files_final holds the final list of config files to pass to the container.
+# You're not meant to override this variable.
+# If you'd like to inject your own arguments, see `matrix_dendrite_app_service_config_files`.
+matrix_dendrite_app_service_config_files_final: "{{ matrix_dendrite_app_service_config_files + matrix_dendrite_app_service_runtime_injected_config_files }}"
+
 # Enable exposure of metrics
 matrix_dendrite_metrics_enabled: false
 matrix_dendrite_metrics_username: "metrics"

roles/matrix-dendrite/templates/dendrite/dendrite.yaml.j2

@@ -145,7 +145,7 @@ app_service_api:
   disable_tls_validation: {{ matrix_dendrite_disable_tls_validation|to_json }}
 
   # Appservice configuration files to load into this homeserver.
-  config_files: {{ matrix_dendrite_app_service_config_files|to_json }}
+  config_files: {{ matrix_dendrite_app_service_config_files_final|to_json }}
 
 # Configuration for the Client API.
 client_api:

roles/matrix-dendrite/templates/dendrite/systemd/matrix-dendrite.service.j2

@@ -41,7 +41,7 @@ ExecStart={{ matrix_host_command_docker }} run --rm --name matrix-dendrite \
 			{% for volume in matrix_dendrite_container_additional_volumes %}
 			-v {{ volume.src }}:{{ volume.dst }}:{{ volume.options }} \
 			{% endfor %}
-			{% for arg in matrix_dendrite_container_extra_arguments %}
+			{% for arg in matrix_dendrite_container_arguments %}
 			{{ arg }} \
 			{% endfor %}
 			{{ matrix_dendrite_docker_image }} \