Move watchtower to a new service

docker-monitoring/docker-compose.yml

@@ -0,0 +1,24 @@
+name: Docker monitoring
+
+services:
+  watchtower:
+    image: containrrr/watchtower
+    environment:
+      DOCKER_HOST: tcp://docker:2375
+      WATCHTOWER_INCLUDE_RESTARTING: true
+      WATCHTOWER_INCLUDE_STOPPED: true
+      WATCHTOWER_MONITOR_ONLY: true
+      WATCHTOWER_NOTIFICATION_URL: /run/secrets/watchtower_notification_url
+    networks:
+      - docker
+    secrets:
+      - watchtower_notification_url
+    restart: unless-stopped
+
+networks:
+  docker:
+    external: true
+
+secrets:
+  watchtower_notification_url:
+    file: ${NASCOMPOSE_SERVICES?}/docker-monitoring/secrets/notification_url