title: Swagger - Formdata with a form-urlEncoded Item
body: <p><br>
  I'm trying to create a swagger document for my api and I'm a little stuck with something that I imagine is quite easy to achieve once you know how.</p>
  
  <p>I have a endpoint that accepts a post as multipart/form-data (As it requires a file upload), however one of those items (pretend it's called "carParts" for the sake of this example), is a FormURLEncodedContent type that is a list of key/value pairs.</p>
  
  <p>So the structure is something like:</p>
  
  <p>carName:ford
  <br>
  carAge:20
  <br>
  carParts:wheels=4&amp;horn=true&amp;windscreen=broken</p>
  
  <p>My problem is that I'm unsure how to express this ("carParts") in the swagger document.</p>
  
  <p>The only way I can see to do it is to set the "carParts" item to a string type, but then I lose the point of swagger, in that I want "wheels", "horn" and "windscreen" to be explicit fields, not just a single form-urlEncoded string.</p>
  
  <p>Is it possible to do this with swagger?</p>
  
  <p>If not, I suppose the only other option is to change my api to just have the "carParts" items as a flat list rather than a structure (i.e. lose the "carParts" parent level and have the items just be other top level formdata items).
  It seems the most straight forward way, but it's a shame if I need to modify the api to achieve this (Not a major issue, just doesn't feel right).</p>