* Use a captcha bypass during registration
The trial initiation flow has a registration step that automatically
does a login in the background. This has Captcha problems, namely that
it can spawn two captchas in a row - one during registration and one
during login. This is not ideal UX, so we've added a bypass token that
returns from the registration endpoint that can be used to skip the next
captcha.
* [review] Introduce ICaptcheProtectedResponse
