Auto-configure synapse-admin to be restricted to a single homeserver (the one managed by the playbook)

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

@@ -30,6 +30,7 @@ ExecStartPre={{ devture_systemd_docker_base_host_command_docker }} create \
 			-p {{ matrix_synapse_admin_container_http_host_bind_port }}:80 \
 			{% endif %}
 			--label-file={{ matrix_synapse_admin_base_path }}/labels \
+			--mount type=bind,src={{ matrix_synapse_admin_config_path }}/config.json,dst=/app/config.json,ro \
 			{% for arg in matrix_synapse_admin_container_extra_arguments %}
 			{{ arg }} \
 			{% endfor %}