v2.6.3

• [EOL] Drop Ruby 3.2 support; require Ruby 3.3+.
• [Maintenance] Align internal naming and YARD docs with the Karafka ecosystem conventions.
• [Maintenance] Drop ostruct from the test dependencies.
• [Fix] Make the Minitest helpers work without Mocha. They no longer fail with undefined method 'stubs' when Mocha is not loaded, and still use Mocha when it is.
• [Fix] Set metadata.message on test messages and give headers: nil empty raw_headers, as a real run does.
• [Fix] Make produce(partition: N) set N as the batch and consumer partition, not only the message one. With mixed partitions the first message decides.