Add support for dynamic informers to kubernetes client

[rohanKanojia]

With introduction of GenericKuberntesResource(equivalent of Unstructured[0] in golang client), we should now able to support dynamic informers[1] with SharedIndexInformer.sharedIndexInformerForCustomResource accepting CustomResourceDefinitionContext.

With just this minor change I was able to get below code working:

diff --git a/kubernetes-client/src/main/java/io/fabric8/kubernetes/client/informers/SharedInformerFactory.java b/kubernetes-client/src/main/java/io/fabric8/kubernetes/client/informers/SharedInformerFactory.java
index f2bf14ca1..8654c7d62 100644
--- a/kubernetes-client/src/main/java/io/fabric8/kubernetes/client/informers/SharedInformerFactory.java
+++ b/kubernetes-client/src/main/java/io/fabric8/kubernetes/client/informers/SharedInformerFactory.java
@@ -152,10 +152,8 @@ public class SharedInformerFactory extends BaseOperation {
    * @param <T> the type parameter (should extend {@link io.fabric8.kubernetes.api.model.HasMetadata} and implement {@link io.fabric8.kubernetes.api.model.Namespaced})
    * @param <L> the type's list parameter (should extend {@link io.fabric8.kubernetes.api.model.KubernetesResourceList}
    * @return the shared index informer
-   * @deprecated Since 5.x versions of client {@link CustomResourceDefinitionContext} are configured via annotations in CustomResource implementations, please use any of the alternative sharedIndexInformerForCustomResource methods
    */
-  @Deprecated
-  public synchronized <T extends CustomResource<?, ?>, L extends KubernetesResourceList<T>> SharedIndexInformer<T> sharedIndexInformerForCustomResource(
+  public synchronized <T extends HasMetadata, L extends KubernetesResourceList<T>> SharedIndexInformer<T> sharedIndexInformerForCustomResource(
     CustomResourceDefinitionContext customResourceContext, Class<T> apiTypeClass, Class<L> apiListTypeClass, long resyncPeriodInMillis) {
     KubernetesDeserializer.registerCustomKind(String.format("%s/%s",
       Objects.requireNonNull(customResourceContext.getGroup()),

Dynamic Informer Sample I tested:

SharedInformerFactory informerFactory = client.informers();
CustomResourceDefinitionContext context = new CustomResourceDefinitionContext.Builder()
        .withGroup("stable.example.com")
        .withVersion("v1")
        .withPlural("crontabs")
        .withScope("Namespaced")
        .build();

SharedIndexInformer<GenericKubernetesResource> informer = informerFactory.sharedIndexInformerForCustomResource(context, GenericKubernetesResource.class, GenericKubernetesResourceList.class, 60 * 1000L);
informer.addEventHandler(new ResourceEventHandler<>() {
    @Override
    public void onAdd(GenericKubernetesResource genericKubernetesResource) {
        System.out.printf("ADD %s", genericKubernetesResource.getMetadata().getName());
    }

    @Override
    public void onUpdate(GenericKubernetesResource genericKubernetesResource, GenericKubernetesResource t1) {
        System.out.printf("UPDATE %s", genericKubernetesResource.getMetadata().getName());
    }

    @Override
    public void onDelete(GenericKubernetesResource genericKubernetesResource, boolean b) {
        System.out.printf("DELETE %s", genericKubernetesResource.getMetadata().getName());
    }
});

informerFactory.startAllRegisteredInformers();

[0] https://github.com/kubernetes/apimachinery/blob/master/pkg/apis/meta/v1/unstructured/unstructured.go#L41
[1] https://firehydrant.io/blog/dynamic-kubernetes-informers/