title: Notification workitem completing without polling on v3
body: <p>it seems that there is a way to achieve non polling mechanism to get the completion of a workitem as said on this page : <a href="https://forge.autodesk.com/en/docs/design-automation/v3/developers_guide/basics/" rel="nofollow noreferrer">https://forge.autodesk.com/en/docs/design-automation/v3/developers_guide/basics/</a>
  But I can't find a way to specify it using the api. What am I supposed to define in the workitem to have a callback on a specific endpoint?</p>
  
  <p>This is what I already have :</p>
  
  <pre><code>var workITem = new WorkItem
              {
                  ActivityId = Services.ForgeService.CleanActivityId,
                  Arguments = new Dictionary&lt;string, IArgument&gt;
                  {
                      {
                          "dwg",
                          new XrefTreeArgument
                          {
                              Url = inputUrl,
                              Verb = Verb.Get
                          }
                      },
                      {
                          "results",
                          new XrefTreeArgument
                          {
                              Verb = Verb.Put,
                              Headers = new Dictionary&lt;string, string&gt;
                              {
                                  {"Authorization", $"Bearer {token}"}
                              },
                              Url = outputUrl
                          }
                      }
                  }
              };
  </code></pre>
  
  <p>Thanks.</p>