Eagerly connect CLI to server when --external-authentication option is used

[findepi]

When CLI is used with password- or kerberos-based auth, it doesn't need to actually make a connection on startup. CLI prints the prompt and authentication happens behind the scenes.

When --external-authentication, the user didn't provide authentication information yet. Printing prompt, and authenticating on first query isn't the best user experience possible.

$ bin/trino-cli --server https://..../ --user piotr@.... --external-authentication
trino> SHOW CATALOGS;
External authentication required. Please go to:
https://.......

Note that when --catalog and --schema are provided, the connection is made eagerly, already, but prints over the prompt:

$ bin/trino-cli --server https://..../ --user piotr@.... --external-authentication --catalog hive --schema default
trino:default> External authentication required. Please go to:
https://.......

[kokosing]

I think it is not only about external authentication. For example one would like to know that the password (or keytab) is invalid eagerly too.

[kokosing]

Oh... that would also verify if the server is up and running too.

[findepi]

@kokosing I agree that it would be better UX overall, but i also am aware the way CLI works was a conscious decision (even if i would make a different one). That's why I would want to focus on --external-authentication case only.

[electrum]

Yes, we should change this for everything, not just authentication.