Nextcloud on UCS - WebApp - logout not working

Nextcloud version: 14
Operating system and version (eg, Ubuntu 17.04): Univenction Corporate Server is running a UNIX-Flavour…

The issue you are facing:

We are developing a Web-Application running on docker, being hosted on UCS. We can use the Login-flow with ease.

-> App Password and Token in combination with username/Password and the Nextcloud Login page

But There is no API-Call to logout and all my attempts at calling the nextclout logout-function

/logout?requesttoken...

failed, due to me not being able to figure out what the token should consist of or how to obtain it…

Can anyone please point me in the right direction? What am I doing wrong? Is there a better approach?

Many thanks for your help in advance!