refresh_token刷新失败

token为同接口authorization_code获取，token能获取收藏及NSFW内容。
测试了是否包含Authorization，同样报错。
测试了是否包含state字段（获取授权时state未保存，此处填写的0），同样报错。
未测试过期token的情况，是此接口仅能刷新过期token嘛？

请求：
```
POST https://bgm.tv/oauth/access_token

header额外包含：User-Agent，Authorization

{"client_id":"bgm******","client_secret":"******","grant_type":"refresh_token","redirect_uri":"https://******","refresh_token":"******"}
```

返回：
`{"error":"invalid_grant","error_description":"Invalid refresh token"}`

Start by tracing the POST /oauth/access_token endpoint and its refresh_token grant handling. Reproduce the request described in the issue and inspect how invalid_grant is produced for a token obtained through authorization_code. Done means determining whether the reported refresh-token use is supported and documenting or correcting the behavior.

Written by the indexing model from the issue text.