multi-part

m_part.FormData form = m_part.FormData.fromMap({
      'first_name': param.firstName,
      'last_name': param.lastName,
    });
    
      form.files.add(
        MapEntry(
          'files[]',
          m_part.MultipartFile.fromBytes(
            post.readAsBytesSync(),
            filename: post.path.split('/').last,
          ),
        ),
      );