Finalises the OpenID authentication by obtaining local authorities for the authenticated user.
The authorities are obtained by calling the configured {@code UserDetailsService}. The {@code UserDetails} it returns must, at minimum, contain the username and {@code GrantedAuthority}objects applicable to the authenticated user. Note that by default, Spring Security ignores the password and enabled/disabled status of the {@code UserDetails} because this is authentication-related and should have beenenforced by another provider server.
The {@code UserDetails} returned by implementations is stored in the generated {@code Authentication} token,so additional properties such as email addresses, telephone numbers etc can easily be stored.
@author Robin Bramley, Opsera Ltd.
@author Luke Taylor