To cancel a reservation (due to timeout or user input), call this. Steam will open a new reservation slot. Note: The user may already be in-flight to your game, so it's possible they will still connect and try to join your party.
Turn off the beacon
async Task<string> JoinAsync()
Will attempt to join the party. If successful will return a connection string. If failed, will return null
When a user follows your beacon, Steam will reserve one of the open party slots for them, and send your game a ReservationNotification callback. When that user joins your party, call OnReservationCompleted to notify Steam that the user has joined successfully