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https://developer.apple.com/videos/play/wwdc2020/10173/ talks about Server notifications for letting a server know, with Sign in with Apple, when changes occur to a user account. I've not been able to find docs online for this. Can you please provide a reference?

This is a copy of a question I've already asked on Stackoverflow-- https://stackoverflow.com/questions/58178187/apple-sign-in-how-to-use-it-for-custom-server-endpoint-authenticationbut I'm posting a summary here too in the hopes of getting some feedback from Apple engineers.My use case is that once I have a user signed into my app, I use the Oauth token, resulting from the sign-in, when I make endpoint calls from my app to my custom server-- to authenticate the caller. E.g., I use Google Sign Inin this way.This method (e.g., with Google Sign In) has several useful properties:1) Updated tokens are created automatically on the client app.2) My custom server can easily verify the validity of the token, using Google's endpoints.3) Initial token verification can take place early in the endpoint request processing-- without access to the custom servers database (as in the style in https://github.com/IBM-Swift/Kitura-Credentials).My question is: Given that we're being told we have to incorporate Apple Sign-In into our iOS apps (if we offer general purpose sign-in facilities), how can I do endpoint authentication with my custom server?(A few more details are on my SO post, linked above).Thanks for your thoughts.