Oauth2 Provider: How To Offer A Login Page In Order To Let Oauth Clients Get The Resource Owner Id

I'm developing a RESTful API in Rails3 and a corresponding OAuth2 provider (consumed by android clients). I supply the typical routes: authorize => Authorization Grant token =

Solution 1:

OK obviously you don't care about authenticating the user on smartphones. At least one should offer and API resource to invalidate an access_token (Logout via App).