Add Key deserializer for KafkaSource

[pierDipi]

This patch adds a KeyDeserializer that uses the
kafkasources.sources.knative.dev/key-type label to
deserialize a record key.

Part of #312

Proposed Changes

• Add Key deserializer for KafkaSource

Release Note

None

Docs

None

[knative-metrics-robot]

The following is the coverage report on the affected files.
Say /test pull-knative-sandbox-eventing-kafka-broker-go-coverage to re-run this coverage report

File	Old Coverage	New Coverage	Delta
control-plane/pkg/reconciler/source/source.go	73.6%	74.5%	1.0

[codecov]

Codecov Report

Merging #1326 (b767833) into main (21930a5) will increase coverage by 0.23%.
The diff coverage is 90.00%.

@@             Coverage Diff              @@
##               main    #1326      +/-   ##
============================================
+ Coverage     75.74%   75.98%   +0.23%     
- Complexity      523      539      +16     
============================================
  Files            94       95       +1     
  Lines          3290     3352      +62     
  Branches        148      154       +6     
============================================
+ Hits           2492     2547      +55     
- Misses          616      619       +3     
- Partials        182      186       +4     

Flag	Coverage Δ
java-unittests	81.11% <87.71%> (+0.12%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...dispatcher/impl/consumer/BaseConsumerVerticle.java	92.85% <ø> (ø)
...ve/eventing/kafka/broker/dispatcher/main/Main.java	0.00% <0.00%> (ø)
.../core/reconciler/impl/ResourcesReconcilerImpl.java	92.02% <50.00%> (-0.68%)	⬇️
...er/impl/consumer/InvalidCloudEventInterceptor.java	92.13% <89.47%> (-1.11%)	⬇️
...oker/dispatcher/impl/consumer/KeyDeserializer.java	93.10% <93.10%> (ø)
control-plane/pkg/core/config/egress.go	100.00% <100.00%> (ø)
control-plane/pkg/reconciler/source/source.go	48.80% <100.00%> (+1.24%)	⬆️
...a/broker/dispatcher/impl/RecordDispatcherImpl.java	82.55% <100.00%> (+0.20%)	⬆️
...patcher/impl/consumer/OrderedConsumerVerticle.java	90.38% <100.00%> (ø)
...r/dispatcher/main/ConsumerVerticleFactoryImpl.java	85.32% <100.00%> (+0.13%)	⬆️

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[matzew]

can we - somewhere, get a little comment/description on the relationship between PARTITION_KEY_EXTENSION and KEY_EXTENSION ?

[pierDipi]

The only reason to use key is for backward compatibility with the exiting source in eventing-kafka.

I'd propose to deprecate that field if possible.

[matzew]

deprecate where? Here? or eventing-kafka ?

[pierDipi]

Both or here only for the future.

There is a bug report related to this knative-extensions/eventing-kafka#897, so even in eventing-kafka to solve that issue and keep backward compatibility, we would need to set the partitionkey extension to the same value of the key extension.

The problem with the key extension is that is Knative specific while partitionkey is a CloudEvent spec thing.

So, I'd deprecate key and the alternative will be partitionkey.

[matzew]

So, I'd deprecate key and the alternative will be partitionkey.

sounds good, @pierDipi

[matzew]

Quite a verbose change, due to signature 😅

But overall looks good - added a few comments

[matzew]

/lgtm
/approve

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[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: matzew, pierDipi

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