I'm using Playfab and Fishnet to create lobbies and matchmaking systems for games like PUBG and Fall guys. In PUBG, when I access the lobby, I see my character standing there, and when I invite my friends, it increases to 4 people. Does a lobby like this require a master server, or do I need to use Relay and Playfab together, or can I just use Playfab and not need a server or host?