Add notification email on invalid second authenticator (#28822)

app/controllers/auth/sessions_controller.rb

@@ -181,6 +181,11 @@ class Auth::SessionsController < Devise::SessionsController
       ip: request.remote_ip,
       user_agent: request.user_agent
     )
+
+    # Only send a notification email every hour at most
+    return if redis.set("2fa_failure_notification:#{user.id}", '1', ex: 1.hour, get: true).present?
+
+    UserMailer.failed_2fa(user, request.remote_ip, request.user_agent, Time.now.utc).deliver_later!
   end
 
   def second_factor_attempts_key(user)