kubernetes: add prometheus scraping annotations

kubernetes/backend-go-service.yaml

@@ -4,6 +4,10 @@ metadata:
   labels:
     app.kubernetes.io/component: backend-go
     app.kubernetes.io/part-of: villas-web
+  annotations:
+    prometheus.io/scrape: 'true'
+    prometheus.io/port: '4000'
+    prometheus.io/path: '/metrics'
   name: backend-go
 spec:
   ports: