chore: refresh automatic content (#709)

Author: mensfeld

Changelog/Rdkafka.md

@@ -4,6 +4,7 @@
 # Rdkafka Changelog
 
 ## Unreleased
+- [Fix] Resolve admin operation handles from the event error when an admin operation fails at the operation level (e.g. brokers unreachable, or the client closed with the request in flight). librdkafka delivers such failures as a result event with the error set and an empty results array, but the create topic, delete topic, create partitions, delete groups, create ACL and delete ACL handlers indexed `results[0]` unconditionally. That raised inside the background event callback, so the handle was never unlocked and `wait` blocked until its own timeout and raised `WaitTimeoutError`, discarding the real error. These handlers now check the event error first and resolve the handle with the actual error code (the describe configs, incremental alter configs, describe ACL and list offsets handlers already did).
 - [Enhancement] Extract the admin background-event result handlers into one class per operation under `lib/rdkafka/callbacks/` (`CreateTopicHandler`, `DescribeConfigsHandler`, etc., all subclasses of `Callbacks::BaseHandler`). `Callbacks::BackgroundEventCallback` is now a thin dispatcher that maps the event type to its handler and destroys the event. Purely internal reorganization (`Rdkafka::Callbacks` is private) with no behavior or API change.
 - [Fix] Destroy admin API background events after processing. librdkafka requires the application to destroy each background event, but `rd_kafka_event_destroy` was never called (nor even bound), so every admin operation leaked its entire result event with all result arrays and strings. Reports are now built inside the callback (copying event-owned memory into Ruby objects) before the event is destroyed, and `DescribeConfigsReport`/`IncrementalAlterConfigsReport` no longer destroy the event-owned ConfigResource array, which also fixes a double free on repeated `wait` calls on the same handle. As part of this, the internal FFI struct fields on admin operation handles (e.g. `handle[:error_string]`, `handle[:result_name]`, `handle[:config_entries]`, `handle[:response_string]`, `handle[:matching_acls]`) were removed; they were never part of the public API (use `handle.wait` and the returned report objects, whose interfaces are unchanged).
 - [Enhancement] Reuse per-thread scratch pointers in `Consumer::Headers.from_native` instead of allocating them for every consumed message. Previously each message paid one native pointer allocation just to check for headers and three more when headers were present; now the scratch pointers are allocated once per thread/fiber and reused, removing all per-message native scratch allocations from the consumer hot path.