AKS - Create dedicated kubernetes service to expose CoreDNS metrics (#2107)

* create service to expose coredns metrics

Signed-off-by: Raul Garcia Sanchez <info@raulgarcia.de>

* create service to expose coredns metrics

Signed-off-by: Raul Garcia Sanchez <info@raulgarcia.de>

---------

Signed-off-by: Raul Garcia Sanchez <info@raulgarcia.de>

jsonnet/kube-prometheus/platforms/aks.libsonnet

@@ -10,4 +10,23 @@
   prometheusAdapter+:: {
     apiService:: null,
   },
+
+  kubernetesControlPlane+: {
+    kubeDnsPrometheusStackService: {
+      apiVersion: 'v1',
+      kind: 'Service',
+      metadata: {
+        name: 'kube-prometheus-stack-coredns',
+        namespace: 'kube-system',
+        labels: { 'k8s-app': 'kube-dns' },
+      },
+      spec: {
+        ports: [
+          { name: 'metrics', port: 9153, targetPort: 9153 },
+        ],
+        selector: { 'k8s-app': 'kube-dns' },
+        clusterIP: 'None',
+      },
+    },
+  },
 }