v0.30.0

• [Feature] Add Admin#alter_consumer_group_offsets and Admin#delete_consumer_group_offsets to set or clear a consumer group's committed offsets from the admin client.
• [Enhancement] Bump the bundled zlib to 1.3.2.
• [Enhancement] Bump librdkafka to 2.15.0.
• [Enhancement] Bump the bundled MIT Kerberos (krb5) to 1.22.2.
• [Enhancement] Add Rdkafka::Config.partitioner_key_uses_bytesize to hash partition keys by byte length, matching other Kafka clients for multibyte keys. Defaults to false.
• [Maintenance] Derive the zlib CHECKSUMS entry from ZLIB_VERSION.
• [Maintenance] Drop the unused dist/openssl-3.0.16.tar.gz build cache.
• [Fix] Honor the isolation_level: argument to Admin#list_offsets, which was silently ignored.
• [Fix] Return correct results for every item of a multi-item topic, partition, group or ACL admin request, not just the first.
• [Maintenance] Fix a use-after-free in the multi-item admin integration test that read result-name pointers after librdkafka had destroyed the background event, which made it flaky on newer glibc (e.g. Debian trixie).
• [Maintenance] Stabilize consumer specs on slow CI runners: wait longer for a partition assignment, raise the TestTopics.create admin timeout (a timeout there also tripped the leaked-handle guard), and let the long-running consumption spec drain its backlog instead of stopping at a fixed 60s.
• [Maintenance] Raise the TestTopics.create admin timeout to 30s so a loaded CI runner no longer hits create topic timed out (which also tripped the leaked-handle guard).