How other players join the host's game

[public-help] One Game Pass covers a group of up to 6: the person who paid plus up to 5 others. The person who paid is the host. They sign in with the email used at checkout, and only they can start a game. Everyone else joins with the game's code and their own email address, confirmed with a one-time code we email them. Joining is free: nobody else needs to buy anything. Everyone needs their own device, because each device holds that player's own clues. In the lobby, each player plays the knock to check their sound, confirms they heard it, then presses 'I'm ready'. The host starts when the group is ready. If a player's code email does not arrive, check spam and check they typed the right address. [internal] Customers may ask: invite friends, my friends cannot get in, join code, game code, do they need to pay, how do the others play, how do I add players.