Merge pull request #60021 from nikhita/sample-controller-subresources

Automatic merge from submit-queue (batch tested with PRs 60102, 59970, 60021, 62011, 62080). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

sample-controller: add status subresource support

Builds on top of https://github.com/kubernetes/kubernetes/pull/55168.

**DO NOT MERGE** until https://github.com/kubernetes/kubernetes/pull/55168 is merged. Adding a hold.
/hold

Update: It is now merged! 🎉

This PR:

- Adds an example to show how to use the `/status` subresource with custom resources.
- Generates `UpdateStatus` for the `Foo` resource.
- Updates the comment in the controller to mention that `UpdateStatus` can now be used. Note: this is not enabled by default because subresources require the feature gate to be enabled and are not on by default.
- Updates the README to add feature gate information and examples for `CustomResourceSubresources`.
- Updates the README to remove feature gate information for CRD validation since the current example uses `apps/v1` deployments (and thus requires v1.9 anyway).

**Release note**:

```release-note
NONE
```

/assign sttts munnerz

Kubernetes-commit: 7bde13f191f0791a87fe5e2575feb3d4849de536

vendor/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured/unstructured.go

@@ -82,7 +82,7 @@ func (obj *Unstructured) EachListItem(fn func(runtime.Object) error) error {
 
 func (obj *Unstructured) UnstructuredContent() map[string]interface{} {
 	if obj.Object == nil {
-		obj.Object = make(map[string]interface{})
+		return make(map[string]interface{})
 	}
 	return obj.Object
 }

vendor/k8s.io/apimachinery/pkg/apis/meta/v1/unstructured/unstructured_list.go

@@ -53,19 +53,18 @@ func (u *UnstructuredList) EachListItem(fn func(runtime.Object) error) error {
 }
 
 // UnstructuredContent returns a map contain an overlay of the Items field onto
-// the Object field. Items always overwrites overlay. Changing "items" in the
-// returned object will affect items in the underlying Items field, but changing
-// the "items" slice itself will have no effect.
-// TODO: expose SetUnstructuredContent on runtime.Unstructured that allows
-// items to be changed.
+// the Object field. Items always overwrites overlay.
 func (u *UnstructuredList) UnstructuredContent() map[string]interface{} {
-	out := u.Object
-	if out == nil {
-		out = make(map[string]interface{})
+	out := make(map[string]interface{}, len(u.Object)+1)
+
+	// shallow copy every property
+	for k, v := range u.Object {
+		out[k] = v
 	}
+
 	items := make([]interface{}, len(u.Items))
 	for i, item := range u.Items {
-		items[i] = item.Object
+		items[i] = item.UnstructuredContent()
 	}
 	out["items"] = items
 	return out