Fix nested entity references

[saschatimme]

This fixes a bug with nested entity references where nested migrations would be dropped.

I think the easiest is to just check the added test case.

Without my fix my test example

{ 
   v: 1,
   c: 4,
   child: {
        v: 1,
        a: 8,
      }
}

would have been migrated to

{ 
   v: 2,
   d: 4,
   child: {
        v: 1,
        a: 8,
      }
}

instead of

{ 
   v: 2,
   d: 4,
   child: {
        v: 2,
        b: 8,
      }
}

sorry for the noisy diff, I don't know which prettier config you use. Maybe you can format the PR?

[AndrewBastin]

Crap, missed this in the Inbox. Will have a look over the weekend @saschatimme 🙇

[AndrewBastin]

lgtm 💯