I'm watching the Sign in with Apple tutorial over and over, and looking at the Juice sample app, and I'm just not seeing where ASPasswordCredential comes into play. I understand it's called via ASAuthorizationPasswordProvider but where is it getting the username and password from? They generically say "icloud keychain".
With a keychain item you generally have a service, account, and optional access group. How do I know what to set those three things to so that Apple knows exactly what is my username and what is my password?