Doxygen pages do not include EDM4hep...

[wdconinc]

Environment: (where does this bug occur, have you tried other environments)

The doxygen pages at https://eic.github.io/EDM4eic/ do not include the EDM4hep classes. This is because we build doxygen documentation inside an alpine container which does not have EDM4hep installed, so the modification to the Doxyfile don't take effect in the GitHub pipelines as they do on a local documentation build.

We could artifact up the EDM4hep include directory from eic-shell in GitHub actions and dump that into the alpine image before running doxygen.

We could also install doxygen into eic-shell and not do anything with alpine.