KIP-282 — Add the listener name to the authentication context

Accepted Kafka 2.0 SecurityBroker

Adds the listener name to the AuthenticationContext passed to Kafka's pluggable PrincipalBuilder, allowing principal mapping logic to vary per listener (e.g., map clients differently on the internal vs external listener). Without the listener name, PrincipalBuilder implementations had to infer the listener from the client's IP address, which is fragile in NAT or load-balanced environments.

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