Thanks for the idea. I found a different idea that might work. I noticed if a user has been migrated then tries to login via a social sign on, I can catch this via account linking.
So, instead of automatic migrations, I could use a bulk migration (which probably would entail some downtime when I roll this out to prod, unfortunately) which would ensure all of our users are in auth0. Then no matter the route of logging in, I should be able to catch an existing user.
What do you think of this idea / do you think it could work?
Thanks!
Luke