- `captcha_solution`: optional, contains provider-specific captcha solution,
- `captcha_token`: optional, contains provider-specific captcha token
- `token`: invite token required when the registrations aren't public.
- `captcha_solution`: optional, contains provider-specific captcha solution,
- `captcha_token`: optional, contains provider-specific captcha token
- `token`: invite token required when the registrations aren't public.