ember-data: loading records in hasMany relationship

I am trying to code feature that allows logged-in users to add products to a "saved item" list. The model is:

//saveditem.js model
export default DS.Model.extend({
    user: belongsTo('user'),
    product: belongsTo('product', { async: true }),
    dateAdded: attr('string')
});

On the saveditems route where the saved items are displayed, the model() hook is:

model() {
    return this.get("store").findAll('saveditem');
}

the api is returning records with JUST the ids:

{
    "dateAdded": "Mon, 11 Dec 2017 20:59:10 GMT",
    "id": 4458,
    "product": 4458,
    "user": "me"
},
{
    "dateAdded": "Sun, 10 Dec 2017 10:26:02 GMT",
    "id": 3657,
    "product": 3657,
    "user": "me"
}
...

How can I get the hasMany relationship to load the actual products, using the IDs?