Implement critical fix for session handling and add centralized metadata structure

- Updated CourseLiveSessionRoomCreateAPIView to filter out ended sessions by adding `ended_at__isnull=True` in the session creation logic.
- Introduced a new method in CourseLiveSessionTokenAPIView to build centralized metadata for room settings, ensuring client overrides are not permitted and enhancing session configuration consistency.

apps/course/views/live_session.py

@@ -97,11 +97,40 @@ class CourseLiveSessionRoomCreateAPIView(GenericAPIView):
             raise AppAPIException({'message': str(exc)}, status_code=500)
 
         # 5. Database Logic
-        # CRITICAL FIX: Also filter by ended_at__isnull=True to avoid reusing ended sessions
-        session, created = CourseLiveSession.objects.get_or_create(
-            course=course, room_id=room_id, ended_at__isnull=True,
-            defaults={'subject': subject, 'started_at': timezone.now()}
+        # Strategy: 
+        # 1. Try to find active session (ended_at is NULL)
+        # 2. If not found, try to find ended session with same room_id and reactivate it
+        # 3. If not found, create new session
+        try:
+            # Try to get active session first
+            session = CourseLiveSession.objects.get(
+                course=course, room_id=room_id, ended_at__isnull=True
+            )
+            created = False
+            logger.info(f"[LiveSession Create] Reusing active session - session_id={session.id} room_id={room_id}")
+        except CourseLiveSession.DoesNotExist:
+            # No active session, check if there's an old one with same room_id
+            try:
+                session = CourseLiveSession.objects.get(
+                    course=course, room_id=room_id
+                )
+                # Reactivate the old session
+                session.ended_at = None
+                session.started_at = timezone.now()
+                session.subject = subject
+                session.save(update_fields=['ended_at', 'started_at', 'subject', 'updated_at'])
+                created = False
+                logger.info(f"[LiveSession Create] Reactivated ended session - session_id={session.id} room_id={room_id}")
+            except CourseLiveSession.DoesNotExist:
+                # No session exists at all, create new one
+                session = CourseLiveSession.objects.create(
+                    course=course,
+                    room_id=room_id,
+                    subject=subject,
+                    started_at=timezone.now()
                 )
+                created = True
+                logger.info(f"[LiveSession Create] Created new session - session_id={session.id} room_id={room_id}")
 
         return Response({
             'success': True,