I am trying to do some research into potentially setting up an existing Drupal site with user accounts/login page to also be an OAuth service provider, basically authenticating users to make calls with a web service. I am looking for a Drupal module which will give this functionality. Most of what I run into are OAuth consumer modules, which is not what I want in this case. I've found a few modules which I think might do this for me, but the module descriptions are generally pretty vague and don't have much of a user base which doesn't inspire much confidence. Has anyone else done this before? What are the best modules available for doing this?