Importing a saved space loses _createTime and overwrites _modTime

Summary: Export a Space. Import it to a new Space. The imported things have no _createTime, and their _modTime is set to the time of Import.

I would expect both to be imported intact - on a low level, yes, the Thing in the new Space has just been both created and modified, but that's on a systems level, not an application level. Conceptually, you haven't created a competely new Thing and then populated it with data, you've imported a pre-existing Thing, and for purposes of the Space's logic that should not register as a change.

(I have very strong feelings that Exporting then Importing a space should not change its data or functionality, particularly if Export is intended as a backup solution. Ideally it should be fully idempotent, too, though I realize that's a stronger ask, and may not be 100% possible given constraints around OIDs.)

If "the time this Thing was imported" is something you ever expect a Space to care about, then I'd advocate for creating either _importTime (specifically for that purpose) or _systemCreateTime / _systemModTime (reflective of low-level values rather than the logical ones - so _systemCreateTime would be set for things like Import or Undelete which definitely should leave _createTime intact), but I'm not coming up with any use-cases.