KIP-729 — Custom validation of records on the broker prior to log append

Discussion Broker

Adds a broker-side plugin interface `RecordInterceptor` (similar to `AuthorizerInterceptor`) that allows custom validation logic to be applied to records before they are appended to the log. There is no mechanism for operators to enforce application-level data quality constraints (e.g., schema compliance) on the broker, forcing consumers to handle malformed records via dead-letter queues or crashes.

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