Rewrite a place.stream.video record in place: retitle, redescribe or retag it, or point it at a finished upload's tracks (publishing them if the upload has none yet: the repair for a record published without tracks, or the way to point a record at a re-finalized VOD). Fields left out are kept; an empty description or tag list clears it. The caller must be the record's owner or hold livestream.manage from them; the record is written with the owner's session.