Make the traceability matrix work in cross-space context
For the moment, the traceability matrix is not cross-space.
Is there a design reason why we didn't do that?
If not, let's do it.
The problem is, the spaceKey is removed when passing to cross-space searches.
This is good because it removes the sidebar,
But it makes other things fail (permission check when retrieving the current space’s saved matrixes).
=> We’ll always execute the cross-space search… in the context of a space. With crossspace=true.