KIP-603 — Change `ConfigEntry` value to use optional fields

Discussion Admin

Changes the return type of `ConfigEntry.value()` in the Admin Client from `String` (nullable) to `Optional<String>` to make the absence of a value explicit in the type system. The current `String` return type silently returns `null` for unset configs, causing NullPointerExceptions in client code that does not defensively check for null.

Protocol Impact

AlterConfigs

Details