Add toJSON() and toMap() support to AccountOwnedModel superclass

[mrashed-dev]

Description

This PR adds a new helper feature that allows all classes that extend AccountOwnedModel to serialize to either a JSON string or a Map representation of the object's fields.

Usage

public class NylasExample {
  public static void main(String[] args) throws Exception {
    NylasClient client = new NylasClient();
    NylasApplication application = client.application("CLIENT_ID", "CLIENT_SECRET");
    Event event = application.events().get("EVENT_ID");

    // Convert Event to JSON
    String eventJSON = event.toJSON();

    // Convert Event to Map
    Map<String, Event> eventMap = event.toMap();
  }
}

License

I confirm that this contribution is made under the terms of the MIT license and that I have the authority necessary to make this contribution on behalf of its copyright owner.