If the SupportVirtualDigipass flag is enabled, this parameter
specifies Perl code that is called whenever a Virtual Digipass tokencode
is to be sent to a user. The hook is expected to transmit the tokencode to
the user over some prompt, secure out-of-band method, such as SMS. The
VirtualTokencodeHook is called like:
VirtualTokencodeHook($self, $username, $tokencode, $p)
VirtualTokencodeHook
must return an error message if it fails to start delivery of the
tokencode the user, otherwise it must return undef.