v0.16.0

• [Breaking] Retire support for Ruby 2.7.
• [Breaking] Messages without headers returned by #poll contain frozen empty hash.
• [Breaking] HashWithSymbolKeysTreatedLikeStrings has been removed so headers are regular hashes with string keys.
• [Feature] Support incremental config describe + alter API.
• [Feature] Oauthbearer token refresh callback (bruce-szalwinski-he)
• [Feature] Provide ability to use topic config on a producer for custom behaviors per dispatch.
• [Enhancement] Use topic config reference cache for messages production to prevent topic objects allocation with each message.
• [Enhancement] Provide Rrdkafka::Admin#describe_errors to get errors descriptions (mensfeld)
• [Enhancement] Replace time poll based wait engine with an event based to improve response times on blocking operations and wait (nijikon + mensfeld)
• [Enhancement] Allow for usage of the second regex engine of librdkafka by setting RDKAFKA_DISABLE_REGEX_EXT during build (mensfeld)
• [Enhancement] name polling Thread as rdkafka.native_kafka#<name> (nijikon)
• [Enhancement] Save two objects on message produced and lower CPU usage on message produced with small improvements.
• [Change] Allow for native kafka thread operations deferring and manual start for consumer, producer and admin.
• [Change] The wait_timeout argument in AbstractHandle.wait method is deprecated and will be removed in future versions without replacement. We don't rely on it's value anymore (nijikon)
• [Fix] Background logger stops working after forking causing memory leaks (mensfeld)
• [Fix] Fix bogus case/when syntax. Levels 1, 2, and 6 previously defaulted to UNKNOWN (jjowdy)