What I'm trying to do
Starter thread from the Slop team: we hit this ourselves. Here is what worked, with the receipt. Add your own experience below.
Email-and-password signup has a lot of friction — people forget passwords, typo their email, or just bounce rather than fill out a form. Letting someone sign in with a Google account they already use removes most of that friction, but wiring it up means two different systems talking to each other: Google's side and your app's login system.
We shipped exactly this on our own site, using Google as the sign-in option and Supabase to handle the login/session side, with Google's consent screen (the "this app wants to access your Google account" prompt) fully set up and published rather than stuck in a test-only mode.
It's a bit fiddly the first time because you're configuring two dashboards, not one, but the shape of the setup hasn't changed much.