The actions of RegistrationUsernameScreen: the method you call on its handle while the screen is open.
Types the username and taps Next. A taken or invalid username is the typed RegistrationUsernameTakenError and the screen stays on top; an accepted one answers the terms screen's handle.
RegistrationUsernameTakenError
The actions of RegistrationUsernameScreen: the method you call on its handle while the screen is open.