Handle in-flight messages during Kafka failover

[peterbroadhurst]

Fix for #43

From the logs you can see Consumer session cleanup happened (due to a Kafka failover event) while there was an in-flight consumer inserting into the receipt store. When it came to acknowledge the message, the session had already been cleaned up.

So we simply need to ignore the request to mark the message - as the session is stale. We will be re-delivered that batch after the consumer session failover completes.

[codecov]

Codecov Report

Merging #44 into master will increase coverage by <.01%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master     #44      +/-   ##
=========================================
+ Coverage    97.6%   97.6%   +<.01%     
=========================================
  Files          48      48              
  Lines        5086    5088       +2     
=========================================
+ Hits         4964    4966       +2     
  Misses         85      85              
  Partials       37      37

Impacted Files	Coverage Δ
internal/kldkafka/client.go	77.77% <100%> (+0.56%)	⬆️

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[jimthematrix]

👍