cubicweb-forge #344907 change the **concerns** relation [open]

I would like a new concerns relation between documentation entities (card, files) and versions. For example, configuration/installation notes can be only pertinent for a given release. And then the content could be better organized by grouping the result set below different titles (from object attributes)

prioritynormal
typeenhancement
done in<not specified>
closed by<not specified>