Add the possibility to pass extra flags to the docker container

roles/matrix-synapse/defaults/main.yml

@@ -24,6 +24,9 @@ matrix_appservice_discord_container_expose_client_server_api_port: false
 # Controls whether the matrix-synapse container exposes the metrics port (tcp/9100).
 matrix_synapse_container_expose_metrics_port: false
 
+# A list of extra arguments to pass to the container
+matrix_synapse_container_extra_arguments: []
+
 # List of systemd services that matrix-synapse.service depends on
 matrix_synapse_systemd_required_services_list: ['docker.service']
 

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

@@ -46,6 +46,9 @@ ExecStart=/usr/bin/docker run --rm --name matrix-synapse \
 			{% for volume in matrix_synapse_container_additional_volumes %}
 			-v {{ volume.src }}:{{ volume.dst }}:{{ volume.options }} \
 			{% endfor %}
+			{% for arg in matrix_synapse_container_extra_arguments %}
+			{{ arg }} \
+			{% endfor %}
 			{{ matrix_synapse_docker_image }} \
 			-m synapse.app.homeserver -c /data/homeserver.yaml