Register a new user, creating them an account.
Registration, when successful, will return an array of access tokens so the user is immediately signed in.
It returns Catalog and Commerce scoped tokens for both Account and Profile. The Commerce ones are intended to allow the purchase of a subscription plan in the step after registration, without the user being prompted to enter their username and password again.
An email will also be sent with a link they need to click to confirm their email address. This confirmation is done via the /verify-email endpoint.