KafkaOperations is missing nullable annotations

[gbaso]

In what version(s) of Spring for Apache Kafka are you seeing this issue?

3.3.3

Describe the bug

KafkaOperations is in a package annotated with @NonNullApi, therefore all method parameters are considered non-nullable, unless annotated differently. KafkaOperations does not have any nullability annotations, despite the data to send being @Nullable in KafkaTemplate.

Expected behavior

KafkaOperations should have nullability annotations similar to KafkaTemplate.

[artembilan]

Confirmed.
For example KafkaTemplate:

	@Override
	public CompletableFuture<SendResult<K, V>> sendDefault(@Nullable V data) {

but KafkaOperations:

CompletableFuture<SendResult<K, V>> sendDefault(V data);

And there are many other similar to this missing annotations.

Please, feel free to contribute the fix: https://github.com/spring-projects/spring-kafka/blob/main/CONTRIBUTING.adoc