支付成功通知接口中有个coupon_fee,看文档说是代金券，但是后台没有设置任何代金券相关配置,请问下官方这个coupon_fee的值从哪里获取的？
cash_fee: '32400',
  coupon_count: '1',
  coupon_fee: '500',
  coupon_fee_0: '500',
  coupon_id_0: '28232857918',  
 nonce_str: '6184a238bd958',
  openid: 'o1ikP0zk9zR1aGgKMRYp7ZSioh4E',
  out_trade_no: 'fu02200024924331636082229976',
  sub_appid: 'wxa4b609d3b2ab57a2',
  sub_mch_id: '1609307152',
  sub_openid: 'oqcny6BN3OLZgaO62_iYCY_cdKP8',
  total_fee: '32900',
  trade_type: 'JSAPI',
  transaction_id: '4200001230202111051204679424'