Add some form of :whoami operation

Connectivity to the server can make use of authentication automatically handled by either the web broswer or in some cases possibly a CLI using a local Kerberos ticket.

This issue is to add a :whoami operation to verify who the connection is running as so the client can see they are connected as the expected user.

Later this may also be expanded to make it possible to query what a client can actually do so operations a client can not perform can be potentially hidden / masked.