@aaronpk This is a great resource, thanks! Is sign-in still working for you, though? I'm seeing the Apple sign-in page throw an error in my testing after I authenticate (though it's possible there's an error in the setup).
“Thankfully, Apple adopted the existing open standards OAuth 2.0 and OpenID Connect to use as the foundation for their new API. While they don’t explicitly call out OAuth or OIDC in their documentation, they use all the same terminology and API calls.”