add DISABLE_UI, DISABLE_ADMIN

pages/404.js

@@ -2,7 +2,11 @@ import React from 'react';
 import Layout from 'components/layout/Layout';
 import { FormattedMessage } from 'react-intl';
 
-export default function Custom404() {
+export default function Custom404({ pageDisabled }) {
+  if (pageDisabled) {
+    return null;
+  }
+
   return (
     <Layout>
       <div className="row justify-content-center">
@@ -13,3 +17,11 @@ export default function Custom404() {
     </Layout>
   );
 }
+
+export async function getServerSideProps() {
+  return {
+    props: {
+      pageDisabled: !!process.env.DISABLE_UI,
+    },
+  };
+}