Consumer Group - Meaningful error on JoinGroupResponse error

[dantswain]

Follow-up task to #219

[dantswain]

I realized I opened this without leaving much of a breadcrumb trail for what actually needs to be done.

kafka_ex/lib/kafka_ex/consumer_group/manager.ex

Line 203 in ede2b09

join_response = %JoinGroupResponse{error_code: :no_error} =

    join_response = %JoinGroupResponse{error_code: :no_error} =
      KafkaEx.join_group(
        join_request,
        worker_name: worker_name,
        timeout: session_timeout + @session_timeout_padding
      )

This will result in a match fail if there is anything other than an "ok" response from the broker, which will crash the worker without much of a useful message to the user. It should at least print out a more meaningful error message and we should evaluate if this really needs to crash the worker.

Additional comments from @joshuawscott #219 (comment)

This will crash if we get any error back from Kafka. I don't know if it's necessarily good to crash within a private function that's in an essentially private module. It will make it difficult to diagnose for a library user. Maybe we should crash with a helpful message here (like display a human-readable version of the error code that we got)

[dantswain]

Closed by #224