Set up discord notification for watchtower

utilities.docker-compose.yml

@@ -6,9 +6,11 @@ services:
       WATCHTOWER_INCLUDE_RESTARTING: true
       WATCHTOWER_INCLUDE_STOPPED: true
       WATCHTOWER_MONITOR_ONLY: true
-      # TODO: Set notification to Discord
+      WATCHTOWER_NOTIFICATION_URL: /run/secrets/watchtower_notification_url
     networks:
       - docker
+    secrets:
+      - watchtower_notification_url
     restart: unless-stopped
 
   smokeping:
@@ -73,3 +75,5 @@ volumes:
 secrets:
   duckdns_token:
     file: ${NASCOMPOSE_SERVICES?}/secrets/duckdns/duckdns_token
+  watchtower_notification_url:
+    file: ${NASCOMPOSE_SERVICES?}/secrets/watchtower/notification_url