✨(backend) give every participant room admin permission

Participants need to be room admin to interact with LiveKit server
api. Until we offer private room, with moderation, all participants
will be considered as room admin.

note: room admin doesn't offer permission to record a room. please,
refer to LiveKit documentation to learn more.

src/backend/core/utils.py

@@ -47,6 +47,7 @@ def generate_token(room: str, user, username: Optional[str] = None) -> str:
     video_grants = VideoGrants(
         room=room,
         room_join=True,
+        room_admin=True,
         can_update_own_metadata=True,
         can_publish_sources=[
             "camera",