Unified Login & Sign-Up: "unknown_user" error is tracked when signing up with Google

[staskus]

The social login failure message is logged when signing up with a Google account that is not associated with the WordPress.com account.

{"success":false,"data":{"errors":[{"code":"unknown_user","message":"Hmm, we can't find a WordPress.com account for that social login. Please double check your information and try again."}]}}

These logs can be misleading when tracking user log in issues.

Steps to reproduce:

1. On the Prologue Screen, tap "Log in or sign up with WordPress.com"
2. Tap Continue with Google.
3. Pick a Google account that is not associated with a WordPress.com account.
4. Notice the Sign-Up Confirmation screen
5. Finish the sign up
6. Open Me
7. Help & Support
8. Application Logs
9. See "Hmm, we can't find a WordPress.com account for that social login. Please double check your information and try again." error

According to these past changes, it should not be happening anymore.

https://user-images.githubusercontent.com/4062343/183646211-0baec5e1-087f-43fe-88cc-a1b76561df65.mov

Same on iOS: