GH-339: RabbitMQ Stream Producer: Initial Support

Resolves https://github.com/spring-cloud/spring-cloud-stream-binder-rabbit/issues/339

* Change waitForConfirms to sync; fix javadoc.

docs/src/main/asciidoc/overview.adoc

@@ -414,8 +414,8 @@ Not supported when the `containerType` is `direct`.
 +
 Default: `1`.
 
-[[rabbitmq-stream]]
-=== Initial Support for the RabbitMQ Stream Plugin
+[[rabbitmq-stream-consumer]]
+=== Initial Consumer Support for the RabbitMQ Stream Plugin
 
 Basic support for the https://rabbitmq.com/stream.html[RabbitMQ Stream Plugin] is now provided.
 To enable this feature, you must add the `spring-rabbit-stream` jar to the class path - it must be the same version as `spring-amqp` and `spring-rabbit`.
@@ -1027,6 +1027,7 @@ public class Application {
 				catch (ExecutionException | TimeoutException e) {
 					throw new IllegalStateException(e);
 				}
+			});
 		};
 	}
 
@@ -1209,3 +1210,38 @@ For negatively acknowledged confirmations, the payload is a `NackedAmqpMessageEx
 
 There is no automatic handling of these exceptions (such as sending to a <<rabbit-dlq-processing, dead-letter queue>>).
 You can consume these exceptions with your own Spring Integration flow.
+
+[[rabbitmq-stream-producer]]
+=== Initial Producer Support for the RabbitMQ Stream Plugin
+
+Basic support for the https://rabbitmq.com/stream.html[RabbitMQ Stream Plugin] is now provided.
+To enable this feature, you must add the `spring-rabbit-stream` jar to the class path - it must be the same version as `spring-amqp` and `spring-rabbit`.
+
+IMPORTANT: The producer properties described above are not supported when you set the `producerType` property to `STREAM_SYNC` or `STREAM_ASYNC`.
+
+To configure the binder to use a stream `ProducerType`, you must add an `Environment` `@Bean` and, optionally, a customizer to customize the message handler.
+
+====
+[source, java]
+----
+@Bean
+Environment streamEnv() {
+    return Environment.builder()
+            .build();
+}
+
+@Bean
+ProducerMessageHandlerCustomizer<MessageHandler> handlerCustomizer() {
+    return (hand, dest) -> {
+        RabbitStreamMessageHandler handler = (RabbitStreamMessageHandler) hand;
+        handler.setConfirmTimeout(5000);
+        ((RabbitStreamTemplate) handler.getStreamOperations()).setProducerCustomizer(
+                (name, builder) -> {
+                    ...
+                });
+    };
+}
+----
+====
+
+Refer to the https://rabbitmq.github.io/rabbitmq-stream-java-client/stable/htmlsingle/[RabbitMQ Stream Java Client documentation] for information about configuring the environment and producer builder.