Sparse fields in nested

[inska]

Hi,

How can I set fields like as below?

Original model:

{
  "key": "ABCD",
  "user": {
    "firstname": "John",
    "lastname": "Smith"
  },
  "created_at": "2018-01"
}

What I want:

{
  "key": "ABCD",
  "user": {
    "firstname": "John",
  },
  "created_at": "2018-01"
}

Can I put the first level keys to fields options?

Thanks,