Create standalone library for epub parsing
Currently kfilemetadata (and thus baloo, dolphin, ...) use libepub from ebook-tools. Okular also uses libepub.
Unfortunately, libepub is unmaintained/dormant for ~5 years, and the library is not very robust when encountering malformed files.
Also, AFAICT it only handles epub 2.0, not epub 3.0/3.2.
A robust and well maintained library would benefit several other KDE projects. Arianna would likely get a much better testing of some of its code, as the parser would be used much more broadly, even by users who don't use Arianna.