Pass data to CreateNewUser action when registering via OAuth

I've got a registration form where the user selects between 2 roles (instructor and learner). Once they have picked, then the rest of the form appears, with options to register via OAuth with Microsoft/GitHub/Google.

I'm after some advice on how to make the selected role be available in CreateNewUser action class, as the user isn't authenticated at the point they click the OAuth link.

This a Jetstream application with teams enabled if that changes anything.