Added postgres database to production and staging

manifests/stage/deployment.yaml

@@ -18,5 +18,11 @@ spec:
           image: registry.internal.uia.no/ikt206-g-26v-devops/group23/flask:latest
           ports:
             - containerPort: 5000
+          env:
+            - name: FLASK_ENV
+              value: staging
+
+            - name: DATABASE_URL
+              value: postgresql://postgres:password@postgres-service:5432/appdb
       imagePullSecrets:
         - name: gitlab-registry-secret