WHY THE FUCK DO YOU FUCKING RETARDS USE TWO DIFFERENT AUTHENTICATION METHODS FOR THE PAYMENT AND THE CHECKOUT API AND DON'T EVEN DOCUMENT THIS SHIT PROPERLY!! 🖕

who offended you so?

Well this is not the only thing about the provider... Also there is a mobile SDK (Android and iOS) and they're full on bugs, hell there is even a memory leak on Android. Just so frustrating to work with this provider and his documentation...