curl --request POST \
  --url https://open.bigmodel.cn/api/paas/v4/files \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: multipart/form-data' \
  --form purpose=batch \
  --form file=@example-file

{
  "id": "<string>",
  "object": "file",
  "bytes": 123,
  "created_at": 123,
  "filename": "<string>",
  "purpose": "<string>"
}