Warden::Manager.after_authentication do |user, auth, options|
  if user.respond_to?(:need_two_step_verification?)
    auth.session(:user)['need_two_step_verification'] = user.need_two_step_verification?
  end
end

Add authentication hook for 2SV
Add authentication hook for 2SV

When a user has been authenticated by Warden using an email address and
passphrase, we set a variable in the session saying that 2SV is
required. This is picked up by the `handle_two_step_verification`
before_action, forcing the user to the 2SV page.
