Amazon Sp Api createFeedDocument，无响应（Node.js）/和InvalidInput contentType错误

我正在尝试将createFeedDocument操作调用到sp api。但我从未得到回应

这是我的签名请求：

 {
  path: '/feeds/2020-09-04/documents',
  method: 'POST',
  host: 'sellingpartnerapi-fe.amazon.com',
  region: 'us-west-2',
  service: 'execute-api',
  headers: {
    'User-Agent': 'MyAmazonApp/1.0 (Language=JavaScript;)',
    'x-amz-access-token': 'Atzasd61as689d1a1f89a189198ea1f891ad89d1e891f89ae189f189165',
    Accept: 'application/json',
    'Accept-Charset': 'utf-8',
    Host: 'sellingpartnerapi-fe.amazon.com',
    'Content-Type': 'application/x-www-form-urlencoded; charset=utf-8',
    'Content-Length': 58,
    'X-Amz-Security-Token': 'Fwa***********************************************',
    'X-Amz-Date': '20210404T230040Z',
    Authorization: 'AWS4-HMAC-SHA256 Credential=ASIASEECTM3DHQOSTQ4M/20210404/us-west-2/execute-api/aws4_request, SignedHeaders=accept;accept-charset;content-length;content-type;host;x-amz-access-token;x-amz-date;x-amz-security-token, Signature=f***********************************************e'
  },
  body: '{"contentType":"text/tab-separated-values; charset=UTF-8"}'
}

如果我尝试调用此操作而不使用body，则会出现如下错误：

{
        "statusCode": 400,
        "res": {
            "errors": [
                {
                    "code": "InvalidInput",
                    "message": "One or more required parameters missing",
                    "details": "contentType;"
                }
            ]
        }
    }

看起来像是sp api上的错误