notify verb should work on authenticated connections only

[sitaram-kalluri]

Describe the bug

• In notify.dart the requireAuth method returns false. This is a bug because the notifications can be sent only on an authenticated connection. So, the requireAuth method should return true.

• In the AbstractVerbHandler.dart, the below condition does not include pol authenticated connections. So, returning "true" from requireAuth might break the working of the notify verb. Modify the below code snippet to process the verb on the pol-authenticated connections.

if (getVerb().requiresAuth() && !atConnectionMetadata.isAuthenticated) {
      throw UnAuthenticatedException('Command cannot be executed without auth');
    }

Steps to reproduce

1. Connection to a secondary server via the terminal
2. Run notify verb (without performing authentication)
3. Notify verb returns "data:null"

Expected behaviour

The notify verb should work on authentication connections only. When attempting to run on an unauthenticated connection an exception should be returned.

[gkc]

A better solution here might be to overhaul the verb permission structure so instead of 'requiresAuth' we flip it to say whether or not the owner, or another atServer, or unauthenticated, can execute the verb.

Also: This isn't important right now