Useless parent_id within inline document.

[ubombi]

Having this value (which is parent _id) make no sense. It should be possible to skip/remove this field from inlined json.

simplified E.G:

{
    "id": 100,
    "inlined": [
        {"id": 1, "parent_id": 100, "value": "foo"},
        {"id": 2, "parent_id": 100, "value": "bar"},
        {"id": 3, "parent_id": 100, "value": "baz"}
    ],
    "field": "value"
}

Technically there is no need for this.