Relate issues inside a project with subprojects
For example, I have a project A with two subprojects A1 and A2.
Relating issues between the two subprojects A1 and A2, I will get the error that
the related issue does not belong to the same project, of course, because it is another subproject.
I know, in Administration -> Settings -> Issue Tracking I can check "Allow cross-project issue relations", but this is not what I want to have, because then I can relate issues between all(!) projects, but I only want between specific (sub)projects.