title: Unauthenticated identites not mapping to Developer Authenticated Identity
body: <p>When a user launches the app they are an unauthenticated user and they receive a <code>unauthenticated cognito identity</code> supplied from the DeveloperAuthenticatedIdentityProvider class in the iOS app.  I can see that <code>unauthenticated cognito identity</code> in the cognito console.  However, when they login and I make a call to my nodejs backend with a logins map of:</p>
  
  <pre><code>{
     DevAuthIdentityLogin:&lt;username&gt;
  }
  </code></pre>
  
  <p>and using this backend code:</p>
  
  <pre><code>getCognitoIdentity: function(logins, cognitoId, error) {
          var cognitoidentity = new AWS.CognitoIdentity(awsOptions);
  
          var params = {
              IdentityPoolId: identityPool,
              Logins: logins,
              TokenDuration: (60 * 5)
          };
  
          cognitoidentity.getOpenIdTokenForDeveloperIdentity(params, function(err, data) {
              if (err) {
                  console.log(err, err.stack);
                  error(err)
              } else {
                  console.log(data);           // successful response
                  cognitoId(data);
              }
          });
      }
  </code></pre>
  
  <p>It creates a new identity id with the <code>developer authenticated identity</code> and I can see that in the cognito console, but the old unauthenticated one is not being mapped to this new developer authenticated one.</p>
  
  <p>Do I need to supply the <code>unauthenticated identity id</code> in the logins map when making a call to my backend to associate the two? OR am I not making this call correctly.  I need some clarification on how to map/merge these identities please.</p>