I am not sure what you have all tried, but it is very possible to login to DocuWare with basic authentication. Check out this post:
There are details on how I use Foxpro to access DocuWare (on-premise, version 6.11).
Long story short, via Postman, if you do a POST with the URL:
you should see XML representing various DocuWare links -- it means you are authenticated. If you do this POST with some sort of persistent connection/request object (such as MSXML2.ServerXMLHTTP
on Windows), you can then do additional GETs to access the various API functions.
Hope this helps!