Imagine an invitation based service which allows only certain email addresses to register and then login.
As developer, I would like to provide a user a simple one-input form at the very beginning of the authentication process. User provides only email address, if email is on a whitelist, user is provided with register or login form.
My question is how can I store the email whitelist and validate if email is ok to login/register before accessing login/register form in auth0?
See https://auth0.com/docs/design/creating-invite-only-applications which gives instructions for invite only flows.
Many SaaS apps allow self-service provisioning, where users can register themselves and begin using the app. Other types of apps, however, do not allow such signups. Instead, the customer (typically an organization of some type) pay upfront for a number of users, and only the end user with the appropriate credentials may sign up and access the app. In such cases, you can use an invite-only workflow for authorization purposes.