User authentication flow: Always redirect with the status

[alveshelio]

Right when authenticating with magic link, if the authentication fails, we get an error

{
"error": "invalid_token",
"error_description": "record not found"
}

And it stays in the Authorizer URL. This isn't very user friendly and it would be nice if it would still redirect but it would pass the response, either success or error and we could handle this in the front-end.

[lakhansamani]

Implemented — verify_email (and the broader MFA-continuation flow) now redirects with status information appended rather than stranding the user on a raw JSON response. Landed in #686.