KafkaSource to implement krshapedlogic

[aliok]

Problem
As suggested here: knative/eventing-contrib#1332 (comment)

Persona:
Which persona is this feature for?

Exit Criteria
A measurable (binary) test that would indicate that the problem has been resolved.

Time Estimate (optional):
How many developer-days do you think this may take to resolve?

Additional context (optional)
Add any other context about the feature request here.

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