fix: rewrite to path expression, if alias for relative is already used in subselect to avoid sql error

[sjvans]

supersedes #116

[schiwekM]

Is the shortcut from #116 maybe still something which could be added? I think most data subjects only have one key and building the subselect directly targeting the data subject would be cheaper to execute and faster in cases where the data subject is multiple relations away.

[sjvans]

Is the shortcut from #116 maybe still something which could be added? I think most data subjects only have one key and building the subselect directly targeting the data subject would be cheaper to execute and faster in cases where the data subject is multiple relations away.

sorry, but not in the short term. i'd rather go in the direction of #123, but not a priority right now.