There are multiple hooks for user registration.
https://usersinsights.com/wp/wp-content/uploads/2018/07/user-registration-hooks-2.png
The `register_post` hook is executed first and
after that there is `registration_errors`.
The captcha verification is done in `registration_errors` hook.
But because we were using `register_post` we were saving
the subscriber before the post request was verified.
[MAILPOET-2114]