Firestore Rules: Limit users using an old version?

Question

I have users using the iOS app from TestFlight that has long been deprecated! Is there a way to block them until they upgrade their app?

I haven't been able to find out documentation about what's inside the request — does anyone have a definitive documentation about this other than the Firebase tutorials? I find the tutorial do not exhaustively cover all the properties of this object and I am curious if there any information about the originating request!

rules_version = '2';

service cloud.firestore {      
  match /databases/{database}/documents {
    match /{document=**} {
        function isBanned(uid) {
                return uid in [
        "3g...V2",
        "z7...w2"
        ];
        }
        allow read, write: if request.auth != null && !isBanned(request.auth.uid);
    }
  }
}