KAFKA-1372: separate 400 error from 500 error in RestClient

[blcksrx]

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[blcksrx]

@kirktrue

[kirktrue]

Thanks for the PR! It looks good to me. You need to get a committer to look at this in order to get it merged in. Perhaps a git blame can turn up someone who's worked on this that you can ping.

[blcksrx]

@mimaison

[mimaison]

Thanks for the PR @blcksrx ! I'll try to take a look in the next few days

[C0urante]

There's also #11844, which addresses the same issue and takes a slightly different approach that preserves the exact status that the client received from the request to the forwarded worker in the response to the REST API.

[C0urante]

BTW, probably want to update the ticket number in the title to 13702.

[mimaison]

We merged #12320, so closing this PR