int | missing | absent

[Antonio via Digitalmars-d-learn]

JSON properties can be
- a value
- null
- absent

What's the standard way to define a serialziable/deserializable 
structs supporting properties of any of this 4 kinds?:

* int
* int | null
* int | absent
* int | null | absent


Whats the best library to manage this JSON requirements? (all the 
4 cases)?


Thanks