code: public static BoxUser createFromId(String userId) {
          JsonObject object = new JsonObject();
          object.add(BoxCollaborator.FIELD_ID, userId);
          object.add(BoxCollaborator.FIELD_TYPE, BoxUser.TYPE);
          BoxUser user = new BoxUser();
          user.createFromJson(object);
          return user;
      }
docs: A convenience method to create an empty user with just the id and type fields set. This allows
  the ability to interact with the content sdk in a more descriptive and type safe manner
  
  @param userId the id of user to create
  @return an empty BoxUser object that only contains id and type information