public function getShoppingCart($entity, $createIfMissing = false)
{
$cart = ShoppingCarts::first(array('conditions' => array('user_id' => $entity->_id, 'status' => 'open')));
if (!isset($cart) and $createIfMissing) {
$cart = ShoppingCarts::create();
$cart->user_id = $entity->_id;
$cart->status = 'open';
$cart->save();
}
return $cart;
}
