Merge pull request #57958 from nikhita/sample-controller-crd-validation

Automatic merge from submit-queue (batch tested with PRs 57902, 57958). 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>.

Add CustomResourceValidation example in sample-controller

Add `CustomResourceValidation` example in sample-controller.

Addresses the following part of https://github.com/kubernetes/sample-controller/issues/2:

> CRDs support json-schema schemas. These CRDs don't have them. It would be nice to show how to add them

**Release note**:

```release-note
NONE
```

/assign sttts munnerz

staging/src/k8s.io/sample-controller/README.md

@@ -73,6 +73,22 @@ type User struct {
 }
 ```
 
+## Validation
+
+To validate custom resources, use the [`CustomResourceValidation`](https://kubernetes.io/docs/tasks/access-kubernetes-api/extend-api-custom-resource-definitions/#validation) feature.
+
+This feature is beta and enabled by default in v1.9. If you are using v1.8, enable the feature using
+the `CustomResourceValidation` feature gate on the [kube-apiserver](https://kubernetes.io/docs/admin/kube-apiserver):
+
+```sh
+--feature-gates=CustomResourceValidation=true
+```
+
+### Example
+
+The schema in the [example CRD](./artifacts/examples/crd.yaml) applies the following validation on the custom resource:
+`spec.replicas` must be an integer and must have a minimum value of 1 and a maximum value of 10.
+
 ## Cleanup
 
 You can clean up the created CustomResourceDefinition with:

staging/src/k8s.io/sample-controller/artifacts/examples/crd.yaml

@@ -9,3 +9,12 @@ spec:
     kind: Foo
     plural: foos
   scope: Namespaced
+  validation:
+    openAPIV3Schema:
+      properties:
+        spec:
+          properties:
+            replicas:
+              type: integer
+              minimum: 1
+              maximum: 10