AprsIsConnection should expose authentication status

Description

AprsIsConnection is gaining the ability to expose if it's logged in with #98, but it should ideally also expose if it is authorized.

For this story, we should change the LoggedIn Boolean to be an enum with states along the lines of NotLoggedIn, Unverified and Verified.

Any CLI code or tests should be updated appropriately.

For reference, the login response message appears to follow the pattern:

# logresp <callsign> <verified|unverified>, server <serverCallsign>

[x] Change LoggedIn boolean to a tri-state enum status reflecting if the client is not logged in, logged in but unverified, or logged in and verified.
[x] Update CLI code, if necessary
[x] Add tests