the API backend should expose an OpenApi (swagger) interface

[duongphuhiep]

if the API endpoint (https://connect2.payxpert.com) exposes an OpenApi (swagger) interface
then you don't evens need to make / maintain any SDK. Because we have the SDK for OpenApi in every language (C#, Python, nodejs, ruby...)

Please consider to put a little effort on the API endpoint, expose it in the Open API, then you can get rid of all the works on SDKs in every languages.