Add password challenge to 2FA settings, e-mail notifications (#11878)

Fix #3961

config/routes.rb

@@ -41,6 +41,7 @@ Rails.application.routes.draw do
 
     namespace :auth do
       resource :setup, only: [:show, :update], controller: :setup
+      resource :challenge, only: [:create], controller: :challenges
     end
   end