Add external monitoring network

coreos-config/plays/services/matrix/docker-compose.yaml

@@ -31,6 +31,7 @@ services:
     networks:
       - default
       - backend
+      - metrics
     labels:
       - "traefik.enable=true"
       - "traefik.http.routers.http-synapse.rule=Host(`synapse.{{ matrix.baseurl }}`)"
@@ -211,6 +212,8 @@ services:
 networks:
   backend:
     internal: true
+  metrics:
+    external: true
 
 volumes:
   synapse_data: