Disable csrf for tutorial react-native app

Tutorial has to send the following header:

"X-Auth": "tutorial_secret"

and then CSRF is ignored.

Author: alexeuler

app/controllers/application_controller.rb

@@ -1,5 +1,6 @@
 class ApplicationController < ActionController::Base
   # Prevent CSRF attacks by raising an exception.
   # For APIs, you may want to use :null_session instead.
-  protect_from_forgery with: :exception
+  protect_from_forgery with: :exception,
+                       if: proc { request.headers["X-Auth"] != "tutorial_secret" }
 end