AMQP: Add bindSourceMessage property (inbound)

Resolves https://github.com/spring-projects/spring-integration/issues/2958

spring-integration-core/src/main/java/org/springframework/integration/IntegrationMessageHeaderAccessor.java

@@ -67,6 +67,11 @@ public class IntegrationMessageHeaderAccessor extends MessageHeaderAccessor {
 
 	public static final String ACKNOWLEDGMENT_CALLBACK = "acknowledgmentCallback";
 
+	/**
+	 * Raw source message.
+	 */
+	public static final String SOURCE_DATA = "sourceData";
+
 	private static final BiFunction<String, String, String> TYPE_VERIFY_MESSAGE_FUNCTION =
 			(name, trailer) -> "The '" + name + trailer;
 
@@ -153,6 +158,18 @@ public class IntegrationMessageHeaderAccessor extends MessageHeaderAccessor {
 		return getHeader(DELIVERY_ATTEMPT, AtomicInteger.class);
 	}
 
+	/**
+	 * Get the source data header, if present.
+	 * @param <T> the data type.
+	 * @return the source header.
+	 * @since 5.1.6
+	 */
+	@SuppressWarnings("unchecked")
+	@Nullable
+	public <T> T getSourceData() {
+		return (T) getHeader(SOURCE_DATA);
+	}
+
 	@SuppressWarnings("unchecked")
 	@Nullable
 	public <T> T getHeader(String key, Class<T> type) {

spring-integration-core/src/main/java/org/springframework/integration/StaticMessageHeaderAccessor.java

@@ -107,4 +107,10 @@ public final class StaticMessageHeaderAccessor {
 				AcknowledgmentCallback.class);
 	}
 
+	@SuppressWarnings("unchecked")
+	@Nullable
+	public static <T> T getSourceData(Message<?> message) {
+		return (T) message.getHeaders().get(IntegrationMessageHeaderAccessor.SOURCE_DATA);
+	}
+
 }