|--AaB03x
      |Content-Disposition: form-data; name="files"
      |Content-Type: multipart/mixed; boundary=BbC04y
      |
      |--BbC04y
      |Content-Disposition: file; filename="file1.txt"
      |Content-Type: text/plain; charset=utf-8
      |
      |... contents of file1.txt ...
      |--BbC04y
      |Content-Disposition: file; filename="file2.gif"
      |Content-Transfer-Encoding: binary