Help implementing Sellsy integration

Hello everyone, i'm in the process of implementing a Sellsy integration on my app which is, for those who don't know, a service to generate and send invoices, estimates etc ... They have an API that i'm using. Right now i'm using the API keys and account the commercial is using for generating its documents but i add "TEST" prefix to the clients i'm working on while developing so it doesnt collide with existing data. My question is more of a