Add documentation for EventHubs (Azure#28673)

Author: dennyac

sdk/eventhubs/azure-messaging-eventhubs/README.md

@@ -342,6 +342,7 @@ EventProcessorClient eventProcessorClient = new EventProcessorClientBuilder()
     .processEvent(eventContext -> {
         System.out.println("Partition id = " + eventContext.getPartitionContext().getPartitionId() + " and "
             + "sequence number of event = " + eventContext.getEventData().getSequenceNumber());
+        eventContext.updateCheckpoint(); // Update checkpoint for this partition.
     })
     .processError(errorContext -> {
         System.out

sdk/eventhubs/azure-messaging-eventhubs/src/main/java/com/azure/messaging/eventhubs/EventHubAsyncClient.java

@@ -115,7 +115,7 @@ EventHubProducerAsyncClient createProducer() {
      * @param consumerGroup The name of the consumer group this consumer is associated with. Events are read in the
      * context of this group. The name of the consumer group that is created by default is
      * {@link EventHubClientBuilder#DEFAULT_CONSUMER_GROUP_NAME "$Default"}.
-     * @param prefetchCount The set of options to apply when creating the consumer.
+     * @param prefetchCount The number of events to queue locally.
      * @return An new {@link EventHubConsumerAsyncClient} that receives events from the Event Hub.
      * @throws NullPointerException If {@code consumerGroup} is {@code null}.
      * @throws IllegalArgumentException If {@code consumerGroup} is an empty string.

sdk/eventhubs/azure-messaging-eventhubs/src/main/java/com/azure/messaging/eventhubs/EventHubClient.java

@@ -79,7 +79,7 @@ EventHubProducerClient createProducer() {
      * @param consumerGroup The name of the consumer group this consumer is associated with. Events are read in the
      *     context of this group. The name of the consumer group that is created by default is {@link
      *     EventHubClientBuilder#DEFAULT_CONSUMER_GROUP_NAME "$Default"}.
-     * @param prefetchCount The set of options to apply when creating the consumer.
+     * @param prefetchCount The number of events to queue locally.
      * @return An new {@link EventHubConsumerClient} that receives events.
      * @throws NullPointerException If {@code consumerGroup} is null.
      * @throws IllegalArgumentException If {@code consumerGroup} is an empty string.