Implement finalizers for GrafanaFolder

[Baarsgaard]

Should close #1680

Testing with the resources in tests/example-resources.yaml

Finalizers are correctly applied and removed on deletion

kubectl apply -f tests/example-resources.yaml
kubectl get grafanafolders.grafana.integreatly.org -o yaml

apiVersion: v1
items:
  - apiVersion: grafana.integreatly.org/v1beta1
    kind: GrafanaFolder
    metadata:
      annotations:
        kubectl.kubernetes.io/last-applied-configuration: |
          {"apiVersion":"grafana.integreatly.org/v1beta1","kind":"GrafanaFolder","metadata":{"annotations":{},"name":"testdata","namespace":"default"},"spec":{"instanceSelector":{"matchLabels":{"test":"testdata"}},"resyncPeriod":"3s","title":"Folder!","uid":"testdata"}}
      creationTimestamp: "2024-12-30T16:44:42Z"
      finalizers:
        - operator.grafana.com/finalizer # <--------
      generation: 1
      name: testdata
      namespace: default
      resourceVersion: "973"
      uid: dd4b350c-f302-410e-93bd-894d34edca2c
    spec:
      allowCrossNamespaceImport: false
      instanceSelector:
        matchLabels:
          test: testdata
      resyncPeriod: 3s
      title: Folder!
      uid: testdata
    status:
      conditions:
        - lastTransitionTime: "2024-12-30T16:45:08Z"
          message: Folder was successfully applied to 1 instances
          observedGeneration: 1
          reason: ApplySuccessful
          status: "True"
          type: FolderSynchronized
      hash: 56e78eb86a0cd663f626b0291607a35d7c8dab8abc91495ed8fe1366c0485d95
      lastResync: "2024-12-30T16:45:14Z"
kind: List
metadata:
  resourceVersion: ""

kubectl delete grafanafolders.grafana.integreatly.org testdata
  grafanafolder.grafana.integreatly.org "testdata" deleted

Finalizers are correctly removed when no grafana instances match

kubectl apply -f tests/example-resources.yaml
kubectl get grafanafolders.grafana.integreatly.org -o yaml

apiVersion: v1
items:
  - apiVersion: grafana.integreatly.org/v1beta1
    kind: GrafanaFolder
    metadata:
      annotations:
        kubectl.kubernetes.io/last-applied-configuration: |
          {"apiVersion":"grafana.integreatly.org/v1beta1","kind":"GrafanaFolder","metadata":{"annotations":{},"name":"testdata","namespace":"default"},"spec":{"instanceSelector":{"matchLabels":{"test":"testdata"}},"resyncPeriod":"3s","title":"Folder!","uid":"testdata"}}
      creationTimestamp: "2024-12-30T16:44:42Z"
      finalizers:
        - operator.grafana.com/finalizer # <--------
      generation: 1
      name: testdata
      namespace: default
      resourceVersion: "973"
      uid: a2af72ab-552b-4763-8d94-5562dbb28128
    spec:
      allowCrossNamespaceImport: false
      instanceSelector:
        matchLabels:
          test: testdata
      resyncPeriod: 3s
      title: Folder!
      uid: testdata
    status:
      conditions:
        - lastTransitionTime: "2024-12-30T16:45:08Z"
          message: Folder was successfully applied to 1 instances
          observedGeneration: 1
          reason: ApplySuccessful
          status: "True"
          type: FolderSynchronized
      hash: 56e78eb86a0cd663f626b0291607a35d7c8dab8abc91495ed8fe1366c0485d95
      lastResync: "2024-12-30T16:45:14Z"
kind: List
metadata:
  resourceVersion: ""

kubectl delete grafanas grafana-testdata
  grafana.grafana.integreatly.org "grafana-testdata" deleted
kubectl get grafanafolders.grafana.integreatly.org -o yaml

apiVersion: v1
items:
  - apiVersion: grafana.integreatly.org/v1beta1
    kind: GrafanaFolder
    metadata:
      annotations:
        kubectl.kubernetes.io/last-applied-configuration: |
          {"apiVersion":"grafana.integreatly.org/v1beta1","kind":"GrafanaFolder","metadata":{"annotations":{},"name":"testdata","namespace":"default"},"spec":{"instanceSelector":{"matchLabels":{"test":"testdata"}},"resyncPeriod":"3s","title":"Folder!","uid":"testdata"}}
      creationTimestamp: "2024-12-30T16:45:46Z"
      generation: 1
      name: testdata
      namespace: default
      resourceVersion: "1204"
      uid: a2af72ab-552b-4763-8d94-5562dbb28128
    spec:
      allowCrossNamespaceImport: false
      instanceSelector:
        matchLabels:
          test: testdata
      resyncPeriod: 3s
      title: Folder!
      uid: testdata
    status:
      NoMatchingInstances: true # <------
      conditions:
        - lastTransitionTime: "2024-12-30T16:46:19Z"
          message: Instances could not be fetched, reconciliation will be retried
          observedGeneration: 1
          reason: EmptyAPIReply
          status: "True"
          type: NoMatchingInstance # <------
      hash: 56e78eb86a0cd663f626b0291607a35d7c8dab8abc91495ed8fe1366c0485d95
      lastResync: "2024-12-30T16:46:24Z"
kind: List
metadata:
  resourceVersion: ""