GroupShare API Documentation

I am in the information gathering phase of a project to incorporate GroupShare into my company's web-based project management software. The bulk of our GroupShare licenses are currently for 2015. I am trying to find some documentation on the different capabilities between the 2015, 2017, and 2019 versions of the GroupShare APIs and I am struggling to find anything of much use.

I do have some familiarity with Trados, but my knowledge of GroupShare is extremely limited as I don't use the SDL software in my role at work.

I've found some links such as http://gs2017dev.sdl.com:41235/docs/ui/index#/ which describe some endpoints for the 2017 version. This is a start, but does not give much context for someone unfamiliar with the software.

Is there any comprehensive documentation available on the web for the different API versions?