docs: item store on @ControllerConfiguration

Author: csviri

Diff for: operator-framework-core/src/main/java/io/javaoperatorsdk/operator/api/reconciler/ControllerConfiguration.java

@@ -128,5 +128,20 @@ MaxReconciliationInterval maxReconciliationInterval() default @MaxReconciliation
    */
   Class<? extends RateLimiter> rateLimiter() default LinearRateLimiter.class;
 
+  /**
+   * Replaces the item store in informer. See underling <a href=
+   * "https://github.com/fabric8io/kubernetes-client/blob/43b67939fde91046ab7fb0c362f500c2b46eb59e/kubernetes-client/src/main/java/io/fabric8/kubernetes/client/informers/impl/DefaultSharedIndexInformer.java#L273">
+   * method</a> in fabric8 client informer implementation.
+   *
+   * The main goal, is to be able to use limited caches.
+   *
+   * See {@link io.javaoperatorsdk.operator.processing.event.source.cache.BoundedItemStore} and
+   * <a href=
+   * "https://github.com/java-operator-sdk/java-operator-sdk/blob/d6eda0138dba6d93c0ff22a5ffcaa7663fa65ca2/caffein-bounded-cache-support/src/main/java/io/javaoperatorsdk/operator/processing/event/source/cache/CaffeinBoundedCache.java">
+   * CaffeinBoundedCache</a>
+   *
+   * @return Optional ItemStore implementation. If present this item store will be used inside the
+   *         informers.
+   */
   Class<? extends ItemStore> itemStore() default ItemStore.class;
 }