JSON API Resources relationship attributes - ruby-on-rails

Question

I have two models related :
class Item < ActiveRecord::Base
belongs_to :carousel
end
And
class Carousel < ActiveRecord::Base
has_many :items
end
I trying to open API to carousels using the JSON API Resources gem, i need to show carousel attributes and some items attributes, something like this:
{
"data": [
{
"id": "1",
"type": "carousels",
"links": {
"self": "http://localhost:3000/api/v1/carousels/1"
},
"attributes": {
"name": "primary",
"items": [
{
"title": "first item",
"file-url": "url",
"index": 0
},
{
"title": "second item",
"file-url": "url",
"index": 1
}
]
}
}
]
}
My carousel resource:
module Api
module V1
class CarouselResource < JSONAPI::Resource
immutable
attributes :name, :items
def self.records(options = {})
user = options[:context][:current_user]
user.carousels
end
end
end
end
My result:
{
"data": [
{
"id": "1",
"type": "carousels",
"links": {
"self": "http://localhost:3000/api/v1/carousels/1"
},
"attributes": {
"name": "primary",
"items": [
{
"id": 3,
"carousel_id": 1,
"file": {
"url": "url"
},
"title": "first item",
"kind": 0,
"index": 0,
"created_at": "2017-02-23T10:31:53.592-03:00",
"updated_at": "2017-03-01T10:30:52.533-03:00"
},
{
"id": 5,
"carousel_id": 1,
"file": {
"url": "url"
},
"title": "second item",
"kind": 0,
"index": 1,
"created_at": "2017-03-01T10:30:07.011-03:00",
"updated_at": "2017-03-01T10:30:07.011-03:00"
}
]
}
}
]
}