This has the benefit of being possible from the _second_ riot instance, which may not actually have the email of the user registering. With these parameters, the RTS can get the email and user ID itself.
(see https://github.com/matrix-org/riot-team-server/pull/15)
Now that the RTS contains config for teams, use GET /teams to get that information so that users will see be able to register as a team (but not yet auto-join rooms, be sent to welcome page or be tracked as a referral).