Allow `@DltHandler` Method to be Defined in a parent class of class annotated with `@KafkaListener`

[JooHyukKim]

Expected Behavior

@DltHandler-annotated method may be in the same class or parent class as the corresponding @KafkaListener annotation.

Current Behavior

@DltHandler-annotated method must be in the same class as the corresponding @KafkaListener annotation.

Context

My usecase is that all our consumer class have their own listener method annotated with @RetryableTopic and @KafkaListener to define per-class specificRetryableTopic.retryTopicSuffix property.
But all @DltHandler methods implementations are exactly the same.
So it would be nice to allow the suggested behavior.

[JooHyukKim]

This sort of offshoot of #3183

[artembilan]

@JooHyukKim ,

The proposal is here: #3464

Thank you for looking into this!

[JooHyukKim]

LGTM, thank you for quick response!