Securing REST API with http auth AND third party OAuth provider

Question

At the moment I have a webapp which offers username/password login or login via Twitter OAuth. I want to add an REST API for this application. Is it possible (and makes it sense) to offer an OAuth login via Twitter for REST API users? Inspired by this post I think about the following authentication flow. Users can login via HTTP authentication AND/OR OAuth:

I created a sample workflow for this problem: http://i.stack.imgur.com/EM446.png

Answer 1

As mentioned in the post you referenced about the authentication flow, you should be looking at OpenID, not OAuth.