title: DocuSign: Is it possible to send a custom payload via PowerForm link and get it back via webhook?
body: <p>I am integrating with DocuSign APIs and I wonder if it's possible to pull off the following scenario:</p>
  
  <ol>
  <li>GET a PowerForm to obtain its URL</li>
  <li>Attach a custom payload to the URL (e.g., some stringified and
  urlencoded JSON)</li>
  <li>Send the URL to a user</li>
  <li>Have the user sign the documents attached to
  the PowerForm's template</li>
  <li>Receive the callback on my webhook</li>
  <li>Recover the custom payload somehow</li>
  </ol>
  
  <p>The context is this: I want to send a specific user a document to sign and when they do it - recognize their specific notification. And this would be a part of a chat over SMS or Skype (chatbot) - so return URL is not really a good option.</p>
  
  <p>I was looking in the direction of Template Custom Fields API because you can in fact fill them using the URL. But it looks like custom fields have to be visible on the document while it is signed and it poses a problem - having something like <code>dfd84fc1-317f-4939-9dfb-4350d2127d2f</code> (even "asterisked") would be a bad UX for the end user.</p>
  
  <p>It's the first time I'm working with DocuSign APIs and so I hope it's just my missing something in the basic concepts... Hence I'm posting this question.</p>