修改用户积分CreditService::getInstance()-UpdateCredit()
兑换成功
gtype
dw_credit_exchange_log插入一条数据
select * from dw_credit_exchange_goods where gstatus=1 and id=$id
gtype==gift
dw_coupon_slot插入一条数据
gtype==voucher
积分兑换流程
修改表dw_credit_exchange_goods的已兑换数量exchanged_num
