feat(grafana): Provision ntfy as a contact point

configuration/services/metrics/grafana.nix

@@ -57,6 +57,19 @@ in
           access = "proxy";
         }
       ];
+
+      alerting.contactPoints.settings.contactPoints = [
+        {
+          name = "ntfy";
+          receivers = [
+            {
+              uid = "ntfy";
+              type = "webhook";
+              settings.url = "http://${config.services.ntfy-sh.settings.listen-http}/local-alerts?template=grafana";
+            }
+          ];
+        }
+      ];
     };
   };