whmcsProxmoxAddon/app/Helper/ErrorCodesLib.php

<?php

namespace ModulesGarden\ProxmoxAddon\App\Helper;

use ModulesGarden\ProxmoxAddon\Core\HandlerError\ErrorCodes\ErrorCodes;

class ErrorCodesLib extends ErrorCodes
{
    const YOUR_APP_000001 = 'Your error message.';
}