[BE] refactor: room users 조회를 웹 소켓 stomp connected인 경우로 변경 (#98)

Signed-off-by: EunJiJung <bianbbc87@gmail.com>

Author: bianbbc87

src/backend/signaling-server/src/main/java/com/asyncgate/signaling_server/security/filter/FilterChannelInterceptor.java

@@ -19,6 +19,8 @@ public class FilterChannelInterceptor implements ChannelInterceptor {
 
     private static final Logger log = LoggerFactory.getLogger(FilterChannelInterceptor.class);
     private static final String AUTHORIZATION_HEADER = "Authorization";
+
+    private static final String ROOM_HEADER = "room-id";
     private static final String BEARER_PREFIX = "Bearer ";
     private final JsonWebTokenUtil jsonWebTokenUtil;
 
@@ -51,7 +53,15 @@ public Message<?> preSend(Message<?> message, MessageChannel channel) {
             if(headerAccessor.getSessionAttributes().get("userId") == null) {
                 throw new ResponseStatusException(HttpStatus.UNAUTHORIZED, "userId is missing");
             }
-            log.info("✅ [STOMP] CONNECT 요청 처리 완료");
+
+            // ✅ roomId 가져오기
+            String roomId = headerAccessor.getFirstNativeHeader(ROOM_HEADER);
+            if (roomId == null || roomId.isEmpty()) {
+                log.error("🚨 [STOMP] Room ID is missing!");
+                throw new ResponseStatusException(HttpStatus.BAD_REQUEST, "Room ID is missing");
+            }
+
+            log.info("✅ [STOMP] CONNECT 요청 처리 완료 - Room ID: {}", roomId);
         }
         return message;
     }