__PACKAGE__->authen->config(
     DRIVER => [ 'DBI',
         DBH         => $dbh,   # provide your own DBI handle
         TABLE       => 'user',
         CONSTRAINTS => { 'user.name'      => '__CREDENTIAL_1__' }
         COLUMNS     => { 'cryptmd5:password' => '__CREDENTIAL_2__' },
         FILTERS     => { cryptmd5 => \&cryptmd5_filter },
     ],
 );