The User Mapping Manager interface provides services for mapping
between a 'user identity' as used when talking to an external
authentication provider, an internal TWiki canonical user ID, and the
displayed name used to identify the user in TWiki. This is the default
TWikiUserMapping in which user information is stored in TWiki topics -
one per user, and then any mapping needed is done using the TWikiUsers
topic in the Main.

WWW: http://twiki.org/cgi-bin/view/Plugins/TWikiUserMappingContrib