title: HTTP POST multipart with named file
body: <p>I need to send a (multipart) HTTP request which contains a file which is named. This seems to be harder to achieve than I imagined... I've tried to figure out a way to do it with HTTPoison, <a href="https://github.com/edgurgel/httpoison/issues/89" rel="nofollow">but I can't get it to use a name other than "file"</a>. I've tried using Hackney directly, <a href="https://github.com/benoitc/hackney/blob/master/doc/hackney.md#request5" rel="nofollow">but there doesn't appear to be an option</a>, and there definitely isn't a test on either of these which shows this functionality. I've also had a look at ibrowse and HTTPotion but can't find anything which seems useful (my Erlang is very limited, mind you). <a href="https://github.com/taf2/curb#http-post-file-upload" rel="nofollow">Here is an example</a> of what I want to do, with the Ruby library Curb (note the Curl::PostField.file takes a name and a file path).</p>
  
  <p>Is this such a strange thing to do? Or am I missing something obvious here... Any suggestion is greatly appreciated.</p>
  
  <p>Thanks!</p>