下载交易账单

curl --location --request POST '/pay/downloadbill' \
--header 'Content-Type: application/xml' \
--data-raw '<?xml version="1.0" encoding="UTF-8"?>
<root>
  <appid>string</appid>
  <bill_date>string</bill_date>
  <bill_type>ALL</bill_type>
  <mch_id>string</mch_id>
  <nonce_str>string</nonce_str>
  <sign>string</sign>
</root>'