Use Redirect URL to identity User

## Is your feature request related to a problem? Please describe

I want to use Apache Answer as my Own Product's Feedback Forum, but user need Register and login. my user already login via Apple Login, I dont want them re-input username and password again.

## Describe the solution you'd like
I want a feautre can login via RedirectURL.

then, I can just put user info in URL and let it click button, and use webview to render apache answer.

user just talk and send his request.

No files, tests, or existing entry points are named. First clarify the redirect-login contract, including how Apple-authenticated user information is conveyed and validated, then define the expected behavior for users opening Apache Answer in a webview.

Written by the indexing model from the issue text.