Implements automatic-kubernetes-api-monitoring-cluster-name feature flag

[mjgrzybek]

Description

AutomaticKubernetesApiMonitoring feature uses clusterLabel to show it on UI.
By default clusterLabel is set to dynakube CR name.
If feature.dynatrace.com/automatic-kubernetes-api-monitoring-cluster-label annotation is set, it's value is used to override default value of clusterLabel.

Unicode characters are supported as a value.

How can this be tested?

kubectl create namespace dynatrace
kubectl apply -f https://github.com/Dynatrace/dynatrace-operator/releases/download/v0.6.0/kubernetes.yaml
kubectl -n dynatrace wait pod --for=condition=ready --selector=app.kubernetes.io/name=dynatrace-operator,app.kubernetes.io/component=webhook --timeout=300s
kubectl apply -f - <<EOF
apiVersion: v1
data:
  apiToken: XXXX
  dataIngestToken: XXXX
kind: Secret
metadata:
  name: dk-4
  namespace: dynatrace
type: Opaque
---
apiVersion: dynatrace.com/v1beta1
kind: DynaKube
metadata:
  name: dk-4
  namespace: dynatrace
  annotations:
    feature.dynatrace.com/automatic-kubernetes-api-monitoring: "true"
    feature.dynatrace.com/automatic-kubernetes-api-monitoring-name: "...dots;;;źdźbło~!🙃."
spec:
  apiUrl: https://xxxxx/api
  activeGate:
    capabilities:
      - routing
      - kubernetes-monitoring
EOF

check if UI shows:

Checklist

• Unit tests have been updated/added
• PR is labeled accordingly

Dismissing my review 'cause issues were fixed