title: Error when calling CreateEnvelope: Invalid Username For Recipient
body: <p>I am using the updated DocuSign API with my .NET application and for the Authentication, I'm using the Authentication Code Grant workflow using 'signature%20extended' as the Code. I can successfully authenticate and get back an access token for the user I'm authenticating with.</p>
  
  <p>I then get the Account details without any issue </p>
  
  <pre><code>ApiClient apiClient = new ApiClient("https://demo.docusign.net/restapi");
  var docuSignUserInfo = apiClient.GetUserInfo(accessToken).Accounts.FirstOrDefault();
  </code></pre>
  
  <p>I then proceed with creating my Signer and Document Model</p>
  
  <pre><code>Document document = new Document
              { DocumentBase64 = Convert.ToBase64String(ReadContent(docName)),
                Name = "Lorem Ipsum", FileExtension = "pdf", DocumentId = "1"
              };
  Document[] documents = new Document[] { document };
  
  // Create the signer recipient object 
              Signer signer = new Signer
              { Email = "test@example.com", FirstName = "Jane", LastName="Doe" ClientUserId = "1000",
                RecipientId = "1", RoutingOrder = "1"
              };
  Signer[] signers = new Signer[] { signer };
  Recipients recipients = new Recipients { Signers = new List&lt;Signer&gt;(signers) };
  
  EnvelopeDefinition envelopeDefinition = new EnvelopeDefinition
              { EmailSubject = "Please sign the document",
                Documents = new List&lt;Document&gt;( documents ),
                Recipients = recipients,
                Status = "sent"
              };
  
  ApiClient apiClient = new ApiClient("https://demo.docusign.net/restapi");
  apiClient.Configuration.AddDefaultHeader("Authorization", "Bearer " + accessToken);
  EnvelopesApi envelopesApi = new EnvelopesApi(apiClient.Configuration);
  
  //This is the API call that throws the error below
  EnvelopeSummary results = envelopesApi.CreateEnvelope(accountId, envelopeDefinition);
  
  
  Error calling CreateEnvelope: {
    "errorCode": "INVALID_USERNAME_FOR_RECIPIENT",
    "message": "The user name for the recipient is invalid. Envelope definition is missing a UserName for recipientId: 1"
  }
  </code></pre>
  
  <p>From my understanding, I shouldn't need to specify any Username/Passwords as I'm using the Access Token for Authentication. Also, I don't understand why a recipient would require a UserName?</p>