/**
 * @swagger
 * components:
 *   schemas:
 *     CartItem:
 *       type: object
 *       required:
 *         - user_id
 *         - product_id
 *         - quantity
 *       properties:
 *         id:
 *           type: integer
 *           description: 购物车商品ID
 *         user_id:
 *           type: integer
 *           description: 用户ID
 *         product_id:
 *           type: integer
 *           description: 商品ID
 *         quantity:
 *           type: integer
 *           description: 商品数量
 *         created_at:
 *           type: string
 *           format: date-time
 *           description: 创建时间
 *         updated_at:
 *           type: string
 *           format: date-time
 *           description: 更新时间
 *     
 *     CartItemWithProduct:
 *       type: object
 *       properties:
 *         id:
 *           type: integer
 *           description: 购物车商品ID
 *         product_id:
 *           type: integer
 *           description: 商品ID
 *         product_name:
 *           type: string
 *           description: 商品名称
 *         quantity:
 *           type: integer
 *           description: 商品数量
 *         points_price:
 *           type: integer
 *           description: 积分价格
 *         rongdou_price:
 *           type: number
 *           description: 融豆价格
 *         image_url:
 *           type: string
 *           description: 商品图片URL
 *         stock:
 *           type: integer
 *           description: 库存数量
 *         payment_methods:
 *           type: array
 *           items:
 *             type: string
 *           description: 支付方式列表
 *         created_at:
 *           type: string
 *           format: date-time
 *           description: 创建时间
 *     
 *     AddToCartRequest:
 *       type: object
 *       required:
 *         - product_id
 *         - quantity
 *       properties:
 *         product_id:
 *           type: integer
 *           description: 商品ID
 *         quantity:
 *           type: integer
 *           minimum: 1
 *           description: 商品数量
 *     
 *     UpdateCartRequest:
 *       type: object
 *       required:
 *         - quantity
 *       properties:
 *         quantity:
 *           type: integer
 *           minimum: 1
 *           description: 商品数量
 */