GH-3119: Add RabbitStreamTemplate.getStreamName()

Fixes: #3119

Without that issues may happen when 'streamName' variable is needed in another stage rather than initialization.

Signed-off-by: Tran Ngoc Nhan <[email protected]>

**Auto-cherry-pick to `3.2.x`**

Author: ngocnhan-tran1996

spring-rabbit-stream/src/main/java/org/springframework/rabbit/stream/producer/RabbitStreamTemplate.java

@@ -230,6 +230,14 @@ public void setObservationConvention(RabbitStreamTemplateObservationConvention o
 		this.observationConvention = observationConvention;
 	}
 
+	/**
+	 * @return the stream name
+	 * @since 3.2.6
+	 */
+	public String getStreamName() {
+		return this.streamName;
+	}
+
 	@Override
 	public MessageConverter messageConverter() {
 		return this.messageConverter;

spring-rabbit-stream/src/test/java/org/springframework/rabbit/stream/producer/RabbitStreamTemplateTests.java

@@ -124,6 +124,7 @@ void superStream() {
 		Producer producer = mock(Producer.class);
 		given(pb.build()).willReturn(producer);
 		try (RabbitStreamTemplate template = new RabbitStreamTemplate(env, "foo")) {
+			assertThat(template.getStreamName()).isEqualTo("foo");
 			SimpleMessageConverter messageConverter = new SimpleMessageConverter();
 			template.setMessageConverter(messageConverter);
 			assertThat(template.messageConverter()).isSameAs(messageConverter);