The way to synchronize several LDAP groups with the same XWiki group is wrong

The authenticator make a synchronization LDAP group by LDAP group in place of grouping them by XWiki group mapping: this means that only the last LDAP group mapping with a XWiki group is taken into account and it also means that the XWiki group is contently modified when a LDAP user is in one of the LDAP groups and not in the other.