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

Fix #3961

app/controllers/auth/challenges_controller.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+class Auth::ChallengesController < ApplicationController
+  include ChallengableConcern
+
+  layout 'auth'
+
+  before_action :authenticate_user!
+
+  skip_before_action :require_functional!
+
+  def create
+    if challenge_passed?
+      session[:challenge_passed_at] = Time.now.utc
+      redirect_to challenge_params[:return_to]
+    else
+      @challenge = Form::Challenge.new(return_to: challenge_params[:return_to])
+      flash.now[:alert] = I18n.t('challenge.invalid_password')
+      render_challenge
+    end
+  end
+end