Adds an SSH key (in the correct format) to the tns user's 'authorized_hosts' file. Optionally, assign/override the 'comment' portion of the entry.
NOTE: The key is a string separated by spaces, containing a type, key, and comment. The "type" inside of the key string must be one of: "ssh-dss" | "ssh-rsa". The "comment" inside the key string is optional but we require the "comment" parameter. If it is empty, we default to the session user's username plus the date.