Allow draft/unpublished on tree-like collections

This seems like an obvious feature that’s probably already in the backlog (as there’s a warning when trying to publish a tree-like collection in draft mode), however, I wanted to make a note that I would like every model type to be draftable, and I’m sure others would too.

Especially useful for navigations with hierarchies where an entire dropdown is auto-published on a specific date when the page is also auto-published (for example).