title: How to set new session id after getting access token in OAuth 2.0
body: <p>I am developing an app for salesforce. For authentication I am using the web server flow. 
  In salesforce OAuth implementation the session id is the same as access token. When I get the new access token (through refresh token method), what's the proper method to pass it to the client. Should I explicitly set the session ID to the new access token? </p>