fix: Copy ClusterClasses and Templates without their owner references (#776)

**What problem does this PR solve?**:
Objects are garbage-collected if owners are not in the target namespace.

Unfortunately, the envtest-based integration tests missed this, because
envtest does not have garbage collection.

I'd like an e2e test to create a cluster in a separate namespace, but
that might in a future PR.

**Which issue(s) this PR fixes**:
Fixes #

**How Has This Been Tested?**:
<!--
Please describe the tests that you ran to verify your changes.
Provide output from the tests and any manual steps needed to replicate
the tests.
-->

**Special notes for your reviewer**:
<!--
Use this to provide any additional information to the reviewers.
This may include:
- Best way to review the PR.
- Where the author wants the most review attention on.
- etc.
-->

Author: dlipovetsky

pkg/controllers/namespacesync/copy.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 
 	corev1 "k8s.io/api/core/v1"
+	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	clusterv1 "sigs.k8s.io/cluster-api/api/v1beta1"
 	"sigs.k8s.io/controller-runtime/pkg/client"
 )
@@ -19,9 +20,7 @@ func copyClusterClassAndTemplates(
 	source *clusterv1.ClusterClass,
 	namespace string,
 ) error {
-	target := source.DeepCopy()
-	target.SetNamespace(namespace)
-	target.SetResourceVersion("")
+	target := copyObjectForCreate(source, source.Name, namespace)
 
 	if err := walkReferences(ctx, target, func(ctx context.Context, ref *corev1.ObjectReference) error {
 		// Get referenced Template
@@ -31,9 +30,7 @@ func copyClusterClassAndTemplates(
 		}
 
 		// Copy Template to target namespace
-		targetTemplate := sourceTemplate.DeepCopy()
-		targetTemplate.SetNamespace(namespace)
-		targetTemplate.SetResourceVersion("")
+		targetTemplate := copyObjectForCreate(sourceTemplate, sourceTemplate.GetName(), namespace)
 
 		if err := w.Create(ctx, targetTemplate); err != nil {
 			return fmt.Errorf(
@@ -63,3 +60,34 @@ func copyClusterClassAndTemplates(
 	}
 	return nil
 }
+
+// copyObjectForCreate copies the object, updating the name and namespace,
+// and preserving only labels and annotations metadata.
+func copyObjectForCreate[T client.Object](src T, name, namespace string) T {
+	dst := src.DeepCopyObject().(T)
+
+	dst.SetName(name)
+	dst.SetNamespace(namespace)
+
+	// Zero out ManagedFields (clients will set them)
+	dst.SetManagedFields(nil)
+	// Zero out OwnerReferences (object is garbage-collected if
+	// owners are not in the target namespace)
+	dst.SetOwnerReferences(nil)
+
+	// Zero out fields that are ignored by the API server on create
+	dst.SetCreationTimestamp(metav1.Time{})
+	dst.SetDeletionGracePeriodSeconds(nil)
+	dst.SetDeletionTimestamp(nil)
+	dst.SetFinalizers(nil)
+	dst.SetGenerateName("")
+	dst.SetGeneration(0)
+	dst.SetLabels(nil)
+	dst.SetManagedFields(nil)
+	dst.SetOwnerReferences(nil)
+	dst.SetResourceVersion("")
+	dst.SetSelfLink("")
+	dst.SetUID("")
+
+	return dst
+}