Very long build times for some Doxygen documentation
The build process for the API documentation of dune-acfem and dune-fem-howto takes extremely long (see e.g. the end of the logs at https://gitlab.dune-project.org/infrastructure/dune-website/-/jobs/15895).
It might be a problem of not guarding the implementation details with
#ifndef DOXYGEN, otherwise I don't understand why the build process takes so much longer than for just dune-fem. Could you please take a look for future releases? With these build times, I'd have reservations about adding a second version of dune-acfem documentation in particular (that docset currently takes 22 minutes to build).