Open requested to merge feature/bin-find-non-tested-headers into master
What this MR does / why does DuMux need it:
Adds a script to determine headers of a dumux project that are not included by its test suite. This could be included into the test suite to ensure that any new header is covered in the test suite.
Before you request a review from someone, make sure to revise the following points:
does the new code follow the style guide?
do the test pipelines pass? (TODO: introduce a fake change to check that selection still works)
is the code you changed and/or the new code you wrote covered in the test suite? (if not, extend the existing tests or write new ones)