Implement OptionAuth for use with DHCPv6 authentication and reconfiguration
The Reconfigure mechanism requires that the server sends Authentication Option (11) to the clients to communicate the authentication key during the Solicit/Reply, Request/Reply and Information-request/Reply transactions. It also uses this option in the Reconfigure messages. The option comprises a record of fields and can't be represented by any of the existing options. The limitation of the OptionCustom class is that the Auth option has the 64-bit field for Replay Detection and OptionCustom does not support 64-bit fields. We could extend the OptionCustom but in fact it is better (and cleaner) to have a dedicated class to represent Auth Option as it has very specific usage and a few convenience functions could be added to this new class to make it easy to manipulate this option. The OptionCustom is very generic.