public function __construct(?string $username = null, ?string $password = null, ?string $domain = null, ?string $apiKey = null) 	{ 		$this->baseUrl = $domain ?? setting('erp_base_url'); 		$this->apiKey = $apiKey ?? setting('erp_api_key'); 		$this->username = $username ?? setting('erp_client_id'); 		$this->password = $password ?? setting('erp_client_secret'); 	}