serialize plain object to multi-level json (`@JsonWrap[ped]`)

```
public class Member{
private String id;
@JsonProperty("User.name")
private String name;
@JsonProperty("User.age")
private Integer age;
}
```
I expect the serialization is
```
{
"id":null,
"User":{
"name":null,
"age": null
}
}
```