There are no instructions here on how to handle the auth0 callback. This is all the text I could fine about the callback
With Auth0, when you log in or sign up, it'll redirect you to Auth0's hosted log-in or sign-up page, then back to your Redwood app. But where in your Redwood app exactly? Auth0 needs to know, and this setting tells it. We'll keep things simple for now and make it "http://localhost:8910", but feel free to configure it as you wish.
Is there another doc I should have read? I’m confused.