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

Fix #3961

spec/mailers/previews/user_mailer_preview.rb

@@ -18,6 +18,21 @@ class UserMailerPreview < ActionMailer::Preview
     UserMailer.password_change(User.first)
   end
 
+  # Preview this email at http://localhost:3000/rails/mailers/user_mailer/two_factor_disabled
+  def two_factor_disabled
+    UserMailer.two_factor_disabled(User.first)
+  end
+
+  # Preview this email at http://localhost:3000/rails/mailers/user_mailer/two_factor_enabled
+  def two_factor_enabled
+    UserMailer.two_factor_enabled(User.first)
+  end
+
+  # Preview this email at http://localhost:3000/rails/mailers/user_mailer/two_factor_recovery_codes_changed
+  def two_factor_recovery_codes_changed
+    UserMailer.two_factor_recovery_codes_changed(User.first)
+  end
+
   # Preview this email at http://localhost:3000/rails/mailers/user_mailer/reconfirmation_instructions
   def reconfirmation_instructions
     user = User.first