Remove cass-operator namespace [K8SSAND-1239] (#387)

* Add patch to `single-namespace` component to remove `cass-operator` namespace.
* Add new kuttl test on ValidatingWebhookConfiguration to make sure it lands in the right namespace.
* Add documentation comments to user-defined-ns test to explain what each step is doing w.r.t. namespacing.

config/components/single-namespace/kustomization.yaml

@@ -22,5 +22,11 @@ replacements:
         kind: ValidatingWebhookConfiguration
       fieldPaths:
       - webhooks.0.clientConfig.service.namespace
-
+patchesStrategicMerge:
+- |-
+  apiVersion: v1
+  kind: Namespace
+  metadata:
+    name: cass-operator
+  $patch: delete
     

test/kuttl/test-user-defined-ns/01-assert.yaml

@@ -14,4 +14,20 @@ status:
   - reason: NewReplicaSetAvailable
     status: "True"
     type: Progressing
-  readyReplicas: 1
+  readyReplicas: 1
+---
+apiVersion: admissionregistration.k8s.io/v1
+kind: ValidatingWebhookConfiguration
+metadata:
+  annotations:
+    cert-manager.io/inject-ca-from: k8ssandra-operator/cass-operator-serving-cert
+  name: cass-operator-validating-webhook-configuration
+webhooks:
+  - admissionReviewVersions:
+      - v1
+      - v1beta1
+    clientConfig:
+      service:
+        name: cass-operator-webhook-service
+        namespace: k8ssandra-operator
+        path: /validate-cassandra-datastax-com-v1beta1-cassandradatacenter

test/kuttl/test-user-defined-ns/01-k8ssandra-operator.yaml

@@ -1,6 +1,8 @@
+# We are deploying a cluster scoped version of cass-operator and k8ssandra-operator into the namespace k8ssandra-operator.
+# This sets us up to ensure the cluster-scope component is successful, and immediately demonstrates that the single-namespace component is sucessful.
 apiVersion: kuttl.dev/v1beta1
 kind: TestStep
 commands: 
 - script: |
     ../../../bin/kustomize build ../../../config/deployments/control-plane/cluster-scope | kubectl apply --server-side --force-conflicts -f -
-  ignoreFailure: false 
+  ignoreFailure: false 

test/kuttl/test-user-defined-ns/02-k8ssandra-cluster.yaml

@@ -1,3 +1,4 @@
+# While all operators are in k8ssandra-operator ns, the K8ssandraCluster is in test-ns. This demonstrates that cluster scoping is successful.
 apiVersion: kuttl.dev/v1beta1
 kind: TestStep
 commands: