Fix Subform JSON needing input ID
- To create a subform it's required the Input's ID which the subform is linked to. But, there's a problem with that: how would front-end know what is the input ID if the input didn't even reach the DB to get an ID in the first place? So it should be possible to create a subform input without the input ID, but it shouldn't break the api or destroy the anti-infinity loop validation.