Install Laravel.

app/Http/Middleware/PreventRequestsDuringMaintenance.php

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+<?php
+
+namespace App\Http\Middleware;
+
+use Illuminate\Foundation\Http\Middleware\PreventRequestsDuringMaintenance as Middleware;
+
+class PreventRequestsDuringMaintenance extends Middleware
+{
+    /**
+     * The URIs that should be reachable while maintenance mode is enabled.
+     *
+     * @var array<int, string>
+     */
+    protected $except = [
+        //
+    ];
+}