Show management only to site admins

api.php

@@ -66,6 +66,10 @@ if ($_SERVER['REQUEST_METHOD'] === 'GET') {
         custom_json(['authenticated' => custom_has_auth_cookie()]);
     }
 
+    if (isset($_GET['adminSession'])) {
+        custom_json(['admin' => custom_is_site_admin()]);
+    }
+
     if (isset($_GET['failMessages'])) {
         custom_json([
             'failMessages' => [