Differentiate between null and missing fields after deserializing

[NehaVDeshmukh]

Currently if we have something like
type A = {
x: string option
y: string option
}
both x and y are deserialized into None type for both cases where they are missing and null in the original json.

There should be an option to deserialize the json such that the null fields are differentiable from the missing fields in the final obj.