public static function fetchForClientUser( ezpRestClient $client, eZUser $user )
    {
        $session = ezcPersistentSessionInstance::get();

        $q = $session->createFindQuery( __CLASS__ );

        $q->where( $q->expr->eq( 'rest_client_id', $q->bindValue( $client->id ) ) )
          ->where( $q->expr->eq( 'user_id', $q->bindValue( $user->attribute( 'contentobject_id' ) ) ) );

        $results = $session->find( $q, __CLASS__ );

        if ( count( $results ) != 1 )
            return false;
        else
            return array_shift( $results );
    }