title: Swashbuckle Swagger generate an actual guid
body: <p>I am using Swashbuckle to generate Swagger in my .Net Core WebAPI project. As you can see below, it generates a GUID of type string. I would like to generate a random Guid and replace "string" with "" or an empty guid "00000000-0000-0000-0000-000000000000". This would allow my example to actually work when I post it.</p>
  
  <pre><code>{
    "payload": [
      {
        "GUID": "string",
        "status": "string"
      }
    ]
  }
  </code></pre>
  
  <p>while I am at it, would it be possible to the same with any string so that JSON is different each time?</p>