[BUG] create helper function ignores the id property when it's equal to 0.

Description :
Create call on a loopback model returns a property id as a response, in case where the property id starts from 0 it is removed from response. This is because the create function( dao.js line no 378) which gets the id as a callback on the create call in a loopback model, does not accepts 0 as an id.

Code snippet from dao.js
if id is 0 it is skipping the if block

function createCallback(err, id, rev) {          
if (id) {
  obj.__data[_idName] = id;
   defineReadonlyProp(obj, _idName, id);
}

We have a scenario where the id starts from 0, and this is causing the id property for our 0th element to be removed from the response.

Steps to reproduce :

• Model which has a property id which starts from 0.
• Call the api to create which will have the id (starting from 0) in response.
• Response will be missing the id property for the first call where id is 0, and it'll add the id property in response starting from id as 1 onwards.

Current Response Behaviour :
id is removed when its value is equal to 0

{
    "property1" : "property1",
   "property2" : "property2"
}

Expected Results :

{
    "id" : 0
    "property1" : "property1",
    "property2" : "property2"
}

Bắt đầu tại hàm createCallback trong dao.js, khoảng dòng 378, và theo dõi cách callback id được gán cho đối tượng được tạo. Tái hiện một lệnh gọi create với id bằng 0, sau đó bổ sung coverage cho phản hồi dự kiến và xác minh rằng các id từ 0 trở lên được giữ nguyên.