[META] How can I link app user with beta tester when using Public Link?

I've decided to use Public Link to get Beta testers on my app. The issue is that I cannot find a way for the users to provide their email or contact info. Therefore I have new users in my database, and new users in App Store Connect but I cannot tell what DB user is link to what App Store Connect user.
I had the idea of having a Beta tester contest to offer reward to the tester with most feedback, but since all the testers on my app are coming from the Public Link, they all show up as 'Anonymous' and there is no way for me to contact them or figure out who is who.
I'm new to TestFlight, am I doing something wrong or is that an inherent drawback of using Public Link?
Has any of you figured out a way to link the App Store Feedback activity to the actual users on your app using Public Link?
Thanks!