Refactor startup modification and environment variable services

Better setup, more flexibility, more tests.

app/Traits/Services/HasUserLevels.php

@@ -0,0 +1,44 @@
+<?php
+
+namespace Pterodactyl\Traits\Services;
+
+use Pterodactyl\Models\User;
+
+trait HasUserLevels
+{
+    /**
+     * @var int
+     */
+    private $userLevel = User::USER_LEVEL_USER;
+
+    /**
+     * Set the access level for running this function.
+     *
+     * @param int $level
+     */
+    public function setUserLevel(int $level)
+    {
+        $this->userLevel = $level;
+    }
+
+    /**
+     * Determine which level this function is running at.
+     *
+     * @return int
+     */
+    public function getUserLevel(): int
+    {
+        return $this->userLevel;
+    }
+
+    /**
+     * Determine if the current user level is set to a specific level.
+     *
+     * @param int $level
+     * @return bool
+     */
+    public function isUserLevel(int $level): bool
+    {
+        return $this->getUserLevel() === $level;
+    }
+}