Use scrapeClass for service monitors

As documented in [1], the platform Prometheus servers are configured
with a scrape class named `tls-client-certificate-auth` which
automatically injects the client certificate and key files for mutual
TLS into the scrape configuration of the service.

This commit also removes the `namespaceSelector` field of the service
monitors: it isn't required when the service monitor and service are
located in the same namespace. It also adjusts the `jobLabel` value to
refer to the `app` label of the service.

[1] https://rhobs-handbook.netlify.app/products/openshiftmonitoring/collecting_metrics.md/#configuring-prometheus-to-scrape-metrics

Signed-off-by: Simon Pasquier <[email protected]>

Author: simonpasquier

manifests/0000_90_etcd-operator_03_servicemonitor.yaml

@@ -8,19 +8,13 @@ metadata:
     include.release.openshift.io/single-node-developer: "true"
 spec:
   endpoints:
-  - bearerTokenFile: /var/run/secrets/kubernetes.io/serviceaccount/token
-    interval: 30s
+  - interval: 30s
     port: https
     scheme: https
     tlsConfig:
-      caFile: /etc/prometheus/configmaps/serving-certs-ca-bundle/service-ca.crt
       serverName: metrics.openshift-etcd-operator.svc
-      certFile: /etc/prometheus/secrets/metrics-client-certs/tls.crt
-      keyFile: /etc/prometheus/secrets/metrics-client-certs/tls.key
-  jobLabel: component
-  namespaceSelector:
-    matchNames:
-    - openshift-etcd-operator
+  jobLabel: app
+  scrapeClass: tls-client-certificate-auth
   selector:
     matchLabels:
       app: etcd-operator