add graphql endpoint

config/routes.rb

@@ -1,11 +1,14 @@
 # frozen_string_literal: true
 Rails.application.routes.draw do
+  mount GraphqlPlayground::Rails::Engine, at: "/playground", graphql_path: "/graphql" if Rails.env.development?
+
+  post "/graphql", to: "graphql#execute"
+
+  devise_for :admin_users
+
   namespace :admin do
     resources :admin_users
 
     root to: "admin_users#index"
   end
-
-  devise_for :admin_users
-  # For details on the DSL available within this file, see https://guides.rubyonrails.org/routing.html
 end