title: how to use retrofit 2 to send file and other params together
body: <p>I am looking for an example how could I send file and other params together to server.</p>
  
  <p>I have to send server JSON which </p>
  
  <pre><code>{
      "title": "title",
      "file": "uploaded file instance",
      "location": {
          "lat": 48.8583,
          "lng": 2.29232,
          "place": "Eiffel Tower"
      }
  }
  </code></pre>
  
  <p>How could I create Retrofit to handle this case?</p>
  
  <p>If file is a string I know how to handle this. If file is File object I have no idea how to do this.</p>