I am trying to implement Sign in with Apple in the Unity editor. I am doing this using the REST API oauth flow.
To use a redirect_uri you need to add it in the configuration of Sign in with Apple in your Service ID as a Return URL. Apple requires that this Return URL cannot be localhost or 127.0.0.1 . In my other oauth implementations I have been able to set a valid redirect url as localhost, so I can catch the response in the app with a http listener. However, Apple does not allow this. The requested authorization code is sent to this redirect_uri, I need to be able to receive this response in the Unity app.
How can I get the response code back in Unity? Sign in with Apple is so new that I have not been able to find any answers so far. All of the guides are for implementing Sign in in a web client, not an app. Apple requires that this code is sent to a web domain, I need it sent to the app instead. How can I do this? I could really use some help here, even just a point in the right direction.