Apple suggests to let users finish in-app purchase first before creating an account. Then take them through adeanonymizationstep afterwards. To do that, what's the best way to identify the unregistered customer? UDID or the original tranaction ID? If use UDID, how can we know the user is actually a customer once they switch to another iphone? Same situation with original tranaction ID maybe?
Ref:https://developer.apple.com/videos/play/wwdc2018/705/?time=1228