Please provide a way to get `authcid` and `authzid`

[TheWaWaR]

After Authenticated, I have to save authcid and authzid for deciding which actions the user are allowed to perform.

Currently, there is no way to get back authcid and authzid from server::ClientFinal since the fields are all private. And also can't call parse_client_first() to get those info since the function is also private.

I suggest provide function for server::ClientFinal to access authcid and authzid.