Register Me

Signs up a caller whose bearer token carries no email address (a sign-in provider that gives none), with the address they type in; every other endpoint answers such a caller 403 with errorCode email_required until they have. The address is unverified: a verification link is sent to it, and it is never used to link the sign-in to an existing account. 201 with the new profile; 409 when the address belongs to an existing account or the caller already has one; 401 without a bearer token (an API key cannot register).