Prometheus monitoring for CoreDNS

Adds a values.yaml api to the CoreDNS chart for configuring prometheus
monitoring service annotations.

Change-Id: I54cee618fc7a0b2f45fe1ef0e9820feccdc73cae

charts/coredns/templates/service.yaml

@@ -6,6 +6,10 @@ metadata:
   labels:
     kubernetes.io/cluster-service: "true"
     kubernetes.io/name: "CoreDNS"
+  annotations:
+{{- if .Values.monitoring.prometheus.enabled }}
+{{ tuple .Values.monitoring.prometheus.coredns | include "helm-toolkit.snippets.prometheus_service_annotations" | indent 4 -}}
+{{- end }}
 spec:
   selector:
     {{ .Values.service.name }}: enabled

charts/coredns/values.yaml

@@ -33,3 +33,10 @@ node_selector: {}
 service:
   name: coredns
   ip: 10.96.0.10
+
+monitoring:
+  prometheus:
+    enabled: false
+    coredns:
+      scrape: true
+      port: 9253