Should users without existing account be bounced to sign up flow?

[ntabris]

When you enter an email address that doesn't correspond to an existing use in a sign in flow, it's not unusual for it to tell you the email doesn't match and to send you to a sign up flow.

For example, here's what Microsoft does (on login.live.com) when you try to sign in with an email it doesn't recognize:

The hosted AuthKit doesn't do this. Instead, it creates the user in WorkOS and completes the login if possible. For instance, if you click social login button on the sign in page, it will create new user and you'll have a successful log in. Obviously you can't directly use email + password (since you don't have a password if there's no user yet), but you can use "Email sign-in code" and use the emailed code to successfully log in.

There are a few reasons why automatically creating the user isn't ideal.

1. For email + password users (i.e., non-social, non-SSO), this means AuthKit/WorkOS never collects the users first and last name.
2. Often people (like me, but I see this with our users as well) forget which email they used for their existing account, and they might try a few different login methods while looking for their existing account. In this case, it's better to say something to the effect of "you don't have an existing account with this email, did you mean to create a new account?" so they know they should try a different email to find their existing account. If a new account is automatically created, it's more likely they'll be confused since they got in... but then their workspace does't have their existing work (so maybe they'll think it got deleted, etc).

It would be nice if the hosted AuthKit (which is really easy to use and integrate with our app!) would support the option to not automatically create new accounts during the sign in flow.