Add sanssh whoami cmd

[sfc-gh-mwojtczak]

Added a new whoami command within sanssh CLI.

This functionality allows users to print their identity details of the current credential source.

Example usage:
sanssh whoami

Example output:

username: sanssh
cert:
        issuer: 
        valid until: 2033-10-16 10:19:03 +0000 UTC (2997 days 16 hours 50 minutes)
groups:
         group1
         group2