API documentation doesn't build

I got a build running on centos7, however the API documentation accessed from Help > User Documentation takes me to a local docs file (file:///home/centos/xstudio/build/bin/docs/user_docs/index.html). From there I can read all the xSTUDIO User Guide documentation, but all API documentation shows a `warning: doxygenfile: Unable to find project ‘xStudio’ in breathe_projects dictionary` for every class/module.

Start by reproducing the API documentation from Help > User Documentation and inspect the generated file at file:///home/centos/xstudio/build/bin/docs/user_docs/index.html. The work is done when the API class and module pages no longer show the reported Breathe project warning.

Written by the indexing model from the issue text.