Correct DeadLetterPublishingRecoverer example to use KafkaOperations

[sh-cho]

DeadLetterPublishingRecoverer ctor cannot take Map<Class<?>, KafkaTemplate<?, ?> as parameter, because constructor is Map<Class<?>, KafkaOperations<? extends Object, ? extends Object>>.

$ ./gradlew build
...

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Compilation failed; see the compiler output below.
  /.../config/KafkaConfig.java:161: error: no suitable constructor found for DeadLetterPublishingRecoverer(Map<Class<?>,KafkaTemplate<?,?>>)
          return new DeadLetterPublishingRecoverer(templates);
                 ^
      constructor DeadLetterPublishingRecoverer.DeadLetterPublishingRecoverer(KafkaOperations<? extends Object,? extends Object>) is not applicable
        (argument mismatch; Map<Class<?>,KafkaTemplate<?,?>> cannot be converted to KafkaOperations<? extends Object,? extends Object>)
      constructor DeadLetterPublishingRecoverer.DeadLetterPublishingRecoverer(Map<Class<?>,KafkaOperations<? extends Object,? extends Object>>) is not applicable
        (argument mismatch; Map<Class<?>,KafkaTemplate<?,?>> cannot be converted to Map<Class<?>,KafkaOperations<? extends Object,? extends Object>>)
  Note: Some messages have been simplified; recompile with -Xdiags:verbose to get full output
  1 error

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BUILD FAILED in 981ms
1 actionable task: 1 executed

I guess type should be like this Map<Class<?>, ? extends KafkaOperations<? extends Object, ? extends Object>> to get KafkaTemplate as parameter, but I'm not sure if changing signature is ok. Overloading is not possible because of type erasure.

So I only updated docs first, to upcast explicitly.

Any opinion would be helpful. Thanks

[sobychacko]

@sh-cho Let's start with the docs on this matter as you did in the PR. Please create an issue so that we can track it. We have the opportunity to cleanup things like these in the 4.0.0 version. Let's re-evaluate it later.

[sh-cho]

@sobychacko Ok. I made an issue

• Change DeadLetterPublishingRecoverer constructor signature to accept ? extends KafkaOperations #3913