title: Swashbuckle.AspNetCore [FromForm]IFormCollection
body: <p>I have the following action in my .NET Core 2 controller. It is an API that should store all data posted as application/x-www-form-urlencoded</p>
  
  <pre><code>[HttpPost("data/add/{formid}"]
  public void Add(int formid, [FromForm]IFormCollection formData) {
      //do something
  }
  </code></pre>
  
  <p>So the Swagger UI allows to try the action using UI:
  <a href="https://i.stack.imgur.com/Gss7k.png" rel="nofollow noreferrer">Swagger UI</a></p>
  
  <p>But the Swagger UI produces POST with body: <strong>formData=field1%3Dvalue1%26field2%3Dvalue2</strong></p>
  
  <p>I expect it to be: <strong>field1=value1&amp;field2=value2</strong></p>
  
  <p>So the question is, is it a limitation of OpenAPI, or a bug of the SwaggerUI? Or maybe there is a way to get what I expect? </p>