cubicweb #1832859 fake HAVING terms w/ EXISTS terms [resolved]

there are cases where we want to use the HAVING trick on terms that should belong to an EXISTS subquery. Currently , this causes bad sql. We should fix that until we've a proper rql grammar avoiding the need for this trick.

Notice at some point, we may want actuall HAVING clauses and GROUPBY used in EXISTS subquery, but that's another story.

done in3.13.2
load left0.000
closed by#f31f9882c90f [rql2sql] closes #1832859: fake HAVING terms w/ EXISTS terms