Implement User Authentication with Sign in with Apple

[codefiesta]

Would it be helpful and useful for OAuthKit to implement / wrap Sign in with Apple using AuthenticationServices or is this out of scope for what OAuthKit does well?

The AuthenticationServices documentation only provides an old-school ViewController approach and really could / should be wrapped into a more modern Observer pattern approach with SwiftUI.

[codefiesta]

It should also be noted that implementing Sign in with Apple only provides identity information from Apple and can't actually issue OAuth tokens for use in subsequent requests. Applications would then need to create an account with that information provided by Apple on their own services.