title: after_create for setting dummy password_digest in case of oauth user with has_secure_password
body: <p>I'm using has_secure_password with a User model. I'd like to set the password_digest string to a dummy value if the user signed up via oauth. Currently, I am only doing facebook and saving the user with facebook_id. I'd like to add the following similar logic:</p>
  
  <pre><code>class User &lt; ActiveRecord::Base
    has_secure_password
    attr_accessible :facebook_id
    after_create :update_password_digest_if_from_facebook
  
    def update_password_digest_if_from_facebook
      logger.info "here within update_password_digest_if_from_facebook" # this gets called
      if self.facebook_id # not seen?
        self.password_digest='oauth-account'
        self.save  
      end
      logger.info "there is a facebook_id" if self.facebook_id # this isn't called 
    end
    ...
  end
  </code></pre>
  
  <p>However, the pieces in update_password_digest_if_from_facebook are not being called correctly. Do I have access to self here?</p>
  
  <p>While this is admittedly a hacky way to bypass has_secure_password, why aren't the calls to self.facebook_id being executed? It seems like I should have access to self at this point.</p>
  
  <p>thx in advance</p>