Thanks Diego medrano.
As per WDC authentication documentation, if authType is basic, Tableau should show a standard username/password dialog, but I am unable to get username/dialog behavior via Tableau Desktop 10.1.5 and tableauwdc-2.2.latest.js. Is this functionality supported on a specific tableau/wdc version?
As per this post https://community.tableau.com/thread/214795, WWW-Authenticate header is not supported in WDC tableau. Can someone please confirm this?