fix Kafka::TransactionManager#send_offsets_to_txn

[stasCF]

• Fix for handling TxnOffsetCommitResponse according to Kafka protocol: https://kafka.apache.org/protocol#The_Messages_TxnOffsetCommit
• Fix for txn_offset_commit: it should be called from group coordinator according to native Java client, otherwise we got an error.

[stasCF]

Hey @dasch, can you give a little advice? I have a failing functional spec for 3 Kafka versions in CircleCI:

wurstmeister/kafka:2.11-0.11.0.3
wurstmeister/kafka:2.11-2.0.1
wurstmeister/kafka:2.12-2.4.0

The problem is I cannot reproduce this fail locally for any of these versions and it appears my code is not related with the failing spec. I run my specs in the same way as in CircleCI step.
What's the next steps should be?

[dasch]

@stasCF sorry about that – the functional specs are unfortunately a bit flaky. I've restarted them.

If someone was inclined to make them more robust I wouldn't at all mind ;)

[dasch]

Code looks good. Have you verified that this branch works in your staging or production setup?

[dasch]

I don't get how this worked in the first place...

[stasCF]

@dasch yes, we run our fork of ruby-kafka in production with this fix included for a couple of weeks and I can confirm it works as expected.

[dasch]

Awesome, thanks!

[dasch]

If you add a line to the changelog I'll go ahead and merge this.

[stasCF]

@dasch done. thanks for your help!