add javadoc to PolicyAnnouncementAcknowledgementAggregatorActor

Signed-off-by: Yannic Klem <yannic.klem@bosch.io>

policies/service/src/main/java/org/eclipse/ditto/policies/service/persistence/actors/announcements/PolicyAnnouncementAcknowledgementAggregatorActor.java

@@ -31,6 +31,15 @@
 import akka.actor.AbstractActorWithTimers;
 import akka.actor.Props;
 
+/**
+ * Aggregates acknowledgements for a published {@link PolicyAnnouncement}
+ * When all acknowledgements are completed the responseConsumer will be called with an {@link Acknowledgements} in case
+ * there are multiple acknowledgements requested or with an {@link Acknowledgement} in case just a single acknowledgement
+ * was requested.
+ * If an error happens the responseConsumer will be called with a {@link DittoRuntimeException}.
+ *
+ * @since 3.0.0
+ */
 final class PolicyAnnouncementAcknowledgementAggregatorActor extends AbstractActorWithTimers {
 
     static final String ACTOR_NAME = "policy-announcement-acknowledgement-aggregator";