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/util/strategicpatch/patch.go

@@ -880,6 +880,29 @@ func StrategicMergeMapPatchUsingLookupPatchMeta(original, patch JSONMap, schema
 	return mergeMap(original, patch, schema, mergeOptions)
 }
 
+// MergeStrategicMergeMapPatchUsingLookupPatchMeta merges strategic merge
+// patches retaining `null` fields and parallel lists. If 2 patches change the
+// same fields and the latter one will override the former one. If you don't
+// want that happen, you need to run func MergingMapsHaveConflicts before
+// merging these patches. Applying the resulting merged merge patch to a JSONMap
+// yields the same as merging each strategic merge patch to the JSONMap in
+// succession.
+func MergeStrategicMergeMapPatchUsingLookupPatchMeta(schema LookupPatchMeta, patches ...JSONMap) (JSONMap, error) {
+	mergeOptions := MergeOptions{
+		MergeParallelList:    false,
+		IgnoreUnmatchedNulls: false,
+	}
+	merged := JSONMap{}
+	var err error
+	for _, patch := range patches {
+		merged, err = mergeMap(merged, patch, schema, mergeOptions)
+		if err != nil {
+			return nil, err
+		}
+	}
+	return merged, nil
+}
+
 // handleDirectiveInMergeMap handles the patch directive when merging 2 maps.
 func handleDirectiveInMergeMap(directive interface{}, patch map[string]interface{}) (map[string]interface{}, error) {
 	if directive == replaceDirective {