Okay, I tried it on my own using a serializer object:
export default DS.RESTSerializer.extend({
serialize: function(snapshot, options) {
var json = this._super(snapshot, options);
json.entity = parseInt(json.entity);
return json;
}
});
However, I do not know if this is the best solution … should also be noted that the documentation of code seems out of date, since the id displayed as numbers and not as strings.