add ENV to filter authorized users

app/controllers/users/omniauth_callbacks_controller.rb

@@ -11,6 +11,11 @@ module Users
       @user = User.from_omniauth(request.env['omniauth.auth'])
 
       if @user.persisted?
+        unless ENV['ALLOWED_BNET_USERS'].split(',').include?(@user.battletag)
+          set_flash_message(:alert, :not_authorized)
+          redirect_to root_path
+          return
+        end
         sign_in_and_redirect @user, event: :authentication
         WowCharactersWorker.perform_async(@user.id)
         WowMountsCollectionWorker.perform_async(@user.id)