guard test mode key only

app/controllers/testing_api_settings_controller.rb

@@ -2,6 +2,8 @@
 
 class TestingApiSettingsController < ApplicationController
   def index
+    raise CanCan::AccessDenied unless current_account.testing?
+
     authorize!(:manage, current_user.access_token)
 
     @webhook_url = current_account.webhook_urls.first_or_initialize