Moving a Page to a new Space doesn't Move it's Unsaved Draft Children and breaks Space Export

1) Create two spaces, ABC and DEF

2) Create a Page "Parent" on space ABC

3) Create a draft under "Parent" on space ABC but don't publish it

4) Move "Parent" to space DEF

5) Do a space export of space ABC, the export has both spaces ABC and DEF

This is because the draft page isn't moved with "Parent", it has a spaceId in space ABC but a parent that's in space DEF. This causes space exports from space ABC to be unusable.