KAFKA-17750: Extend kafka-consumer-groups command line tool to support new consumer group

[FrankYang0529]

The new consumer groups have more state available to troubleshoot issues. For instance, each member has an epoch, an assignment, a target assignment, etc. It would be useful to display those too in order to give administrator a detailed view of the state of the groups.

KIP: https://cwiki.apache.org/confluence/display/KAFKA/KIP-1099%3A+Extend+kafka-consumer-groups+command+line+tool+to+support+new+consumer+group

Committer Checklist (excluded from commit message)

• Verify design and implementation
• Verify test coverage and CI build status
• Verify documentation (including upgrade notes)

[dajac]

@FrankYang0529 Thanks for the patch. I can help reviewing it. However, would it be possible to split in 2 or 3 PRs? Small PRs are easier to review. We could have one for the API (schema + server changes), one for the admin client and finally one for the tool. What do you think?

[FrankYang0529]

Hi @dajac, thanks for the suggestion. I will close this one and split to multiple PRs. 👍

[FrankYang0529]

• API (schema + server changes): KAFKA-17750: Extend kafka-consumer-groups command line tool to support new consumer group (part 1) #17958
• Admin client: KAFKA-17750: Extend kafka-consumer-groups command line tool to support new consumer group (part 2) #18034
• Tool: WIP