Document `AUTH_<PROVIDER>_ALLOW_PUBLIC_REGISTRATION` for public sso user registration about directus

[rijkvanzanten]

Thanks for the suggestion! I've updated it in the linked PR

Also worth mentioning that the error that pops up otherwise "invalid credentials" is not helpful, not at all.

Can't do much about that unfortunately. Showing the difference in error during login results in a security vulnerability similar to GHSA-jgf4-vwc3-r46v

[Jan0707]

Okay, I have been banging my head against this for two days wondering what was wrong with my setup. And THIS was the solution. IMHO this needs to be added to the documentation ASAP.

Also worth mentioning that the error that pops up otherwise "invalid credentials" is not helpful, not at all.

Thank you very much @j0weiss !