MINOR: Cleanup in SharePartition acknowledgement functionality

[adixitconfluent]

About

This PR performs cleanup in SharePartition.java acknowledgement flow. We do not need Objects.requireNonNull(recordState); firstly because this has been covered in this code. Also throwing a NullPointerException is indeed wrong for an invalid acknowledge type provided by the client.

Testing

Added some unit tests.

[apoorvmittal10]

Looks good, minor comment.

[apoorvmittal10]

RecordState recordState = Objects.requireNonNull(ACK_TYPE_TO_RECORD_STATE.get(ackType));

[adixitconfluent]

I don't think we require Objects.requireNonNull()since this code would be covered when we perform fetchAckTypeMapForBatch and it should be covered there. Hence, I thought to remove it.

[apoorvmittal10]

For now ofcourse yes, but the check was placed so one do not forget to update the ACK_TYPE_TO_RECORD_STATE map while adding new values.

[adixitconfluent]

then maybe lets not have Objects.requireNonNull since it throws a NullPointerException, rather we throw an IllegalRequestException or InvalidRequestException, wdyt?

[apoorvmittal10]

Anything is fine but some exception should highlight the map is missing the required value.

[adixitconfluent]

done

[AndrewJSchofield]

Thanks for the PR. Looks good to me.

[apoorvmittal10]

Thanks for the change, LGTM!