isNew (opts) {
    return utils.get(this, this._mapper().idAttribute) === undefined
  }
Return whether the record is unsaved. Records that have primary keys are
considered "saved". Records without primary keys are considered "unsaved".

@example <caption>Record#isNew</caption>
const JSData = require('js-data');
const { Container } = JSData;
console.log('Using JSData v' + JSData.version.full);
const store = new Container();
store.defineMapper('user');
const user = store.createRecord('user', {
  id: 1234
});
const user2 = store.createRecord('user');
console.log('user isNew: ' + user.isNew()); // false
console.log('user2 isNew: ' + user2.isNew()); // true

@method Record#isNew
@returns {boolean} Whether the record is unsaved.
@since 3.0.0