Always set heart-beat header in STOMP CONNECTED frames

Since SPR-10954, the SimpleBrokerMessageHandler supports `heart-beats`.

Even if the STOMP spec states that the `heart-beat` header is OPTIONAL,
and if absent considered as `heart-beat: 0,0`,
some clients rely on this to be set in CONNECTED frames.

This commit adds this header information even if no task
scheduler/heart-beat have been configured.

See: https://stomp.github.io/stomp-specification-1.2.html#Heart-beating

Issue: SPR-10954

spring-websocket/src/main/java/org/springframework/web/socket/messaging/StompSubProtocolHandler.java

@@ -449,6 +449,8 @@ public class StompSubProtocolHandler implements SubProtocolHandler, ApplicationE
 		long[] heartbeat = (long[]) connectAckHeaders.getHeader(SimpMessageHeaderAccessor.HEART_BEAT_HEADER);
 		if (heartbeat != null) {
 			connectedHeaders.setHeartbeat(heartbeat[0], heartbeat[1]);
+		} else {
+			connectedHeaders.setHeartbeat(0, 0);
 		}
 		return connectedHeaders;
 	}

spring-websocket/src/test/java/org/springframework/web/socket/messaging/StompSubProtocolHandlerTests.java

@@ -150,6 +150,25 @@ public class StompSubProtocolHandlerTests {
 				"user-name:joe\n" + "\n" + "\u0000", actual.getPayload());
 	}
 
+	@Test
+	public void handleMessageToClientWithSimpConnectAckDefaultHeartBeat() {
+
+		StompHeaderAccessor accessor = StompHeaderAccessor.create(StompCommand.CONNECT);
+		accessor.setHeartbeat(10000, 10000);
+		accessor.setAcceptVersion("1.0,1.1");
+		Message<?> connectMessage = MessageBuilder.createMessage(EMPTY_PAYLOAD, accessor.getMessageHeaders());
+
+		SimpMessageHeaderAccessor ackAccessor = SimpMessageHeaderAccessor.create(SimpMessageType.CONNECT_ACK);
+		ackAccessor.setHeader(SimpMessageHeaderAccessor.CONNECT_MESSAGE_HEADER, connectMessage);
+		Message<byte[]> ackMessage = MessageBuilder.createMessage(EMPTY_PAYLOAD, ackAccessor.getMessageHeaders());
+		this.protocolHandler.handleMessageToClient(this.session, ackMessage);
+
+		assertEquals(1, this.session.getSentMessages().size());
+		TextMessage actual = (TextMessage) this.session.getSentMessages().get(0);
+		assertEquals("CONNECTED\n" + "version:1.1\n" + "heart-beat:0,0\n" +
+				"user-name:joe\n" + "\n" + "\u0000", actual.getPayload());
+	}
+
 	@Test
 	public void handleMessageToClientWithSimpHeartbeat() {