public static function getDefaultConfiguration($handler = null)
    {
        $config = [
            'headers' => [
                'Accept' => 'application/json',
                'Content-Type' => 'application/json',
            ],
        ];

        if (!$handler) {
            $handler = HandlerStack::create();
            $handler->push(Middleware::mpxErrors(), 'mpx_errors');
        }
        $config['handler'] = $handler;

        return $config;
    }