uploadPart method
Implementation
HttpRequest uploadPart(String bucketName, String fileKey, String uploadId,
int partNumber, List<int> data) {
final url = "https://${bucketName}.${this.endpoint}/${fileKey}";
final params = <String, dynamic>{"partNumber": '$partNumber', "uploadId": uploadId};
HttpRequest req = HttpRequest(url, 'PUT', params, <String, String>{});
req.fileData = data;
this._auth!.signRequest(req, bucketName, fileKey);
return req;
}