Allow multiple credentials for a single hostname

[cmessick]

Description

As a user, I'd like to be able to specify multiple credentials for a single hostname. I'm trying to listen to two separate topics on gcn-kafka that have the same hostname but separate credentials. Is that possible?

[cnweaver]

This should already be supported:

(hop-client) $ hop auth add                                                                                                                                                                                                          
2023-04-07 19:43:23,047 | hop : INFO : Generating configuration with user-specified username + password
Username: user-1
Password: 
Hostname (may be empty): example.com
Token endpoint (empty if not applicable): 
2023-04-07 19:43:37,871 | hop : INFO : Wrote configuration to: /Users/christopher/.config/hop/auth.toml
(hop-client) $ hop auth add                                                                                                                                                                                                          
2023-04-07 19:43:40,791 | hop : INFO : Generating configuration with user-specified username + password
Username: user-2
Password: 
Hostname (may be empty): example.com
Token endpoint (empty if not applicable): 
2023-04-07 19:43:52,645 | hop : INFO : Wrote configuration to: /Users/christopher/.config/hop/auth.toml
(hop-client) $ hop auth list                                                                                                                                                                                                         
user-1 for example.com
user-2 for example.com
(hop-client) $ hop list-topics kafka://[email protected]  # Should attempt to connect as user-1

[cmessick]

@cnweaver It looks like that requires specifying specific users though. Unfortunately, the usernames generated by GCN-Kafka are randomly generated, and will be different across different deployments, so we don't have an easy way to implement specifying usernames at the stage where we instantiate the consumers and producers.