review fix

After kafka client 2.4 producer uses sticky partition, its randomly chose partition and topic default partitions is 2, configure that @embeddedkafka to provide just one partition per topic.

* javadoc in `AsyncRepliesAware`
* fix test in EnableKafkaKotlinCoroutinesTests
* polish adoc

spring-kafka-docs/src/main/antora/modules/ROOT/pages/kafka/receiving-messages/async-returns.adoc

@@ -2,7 +2,7 @@
 = Asynchronous `@KafkaListener` Return Types
 
 `@KafkaListener` (and `@KafkaHandler`) methods can be specified with asynchronous return types, letting the reply be sent asynchronously.
-return types include `CompletableFuture<?>`, `Mono<?>` and Kotlin `suspend` functions
+return types include `CompletableFuture<?>`, `Mono<?>` and Kotlin `suspend` functions.
 
 [source, java]
 ----

spring-kafka-docs/src/main/antora/modules/ROOT/pages/whats-new.adoc

@@ -17,5 +17,5 @@ See xref:kafka/transactions.adoc#transaction-id-suffix-fixed[Fixed TransactionId
 [[x32-async-return]]
 === Async @KafkaListener Return
 
-`@KafkaListener` (and `@KafkaHandler`) methods can now return asynchronous return types `CompletableFuture<?>` and `Mono<?>`.
+`@KafkaListener` (and `@KafkaHandler`) methods can now return asynchronous return types include `CompletableFuture<?>`, `Mono<?>` and Kotlin `suspend` functions.
 See xref:kafka/receiving-messages/async-returns.adoc[Async Returns] for more information.

spring-kafka/src/main/java/org/springframework/kafka/listener/adapter/AsyncRepliesAware.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2023 the original author or authors.
+ * Copyright 2023-2024 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,15 +17,16 @@
 package org.springframework.kafka.listener.adapter;
 
 /**
- * Auto-detect {@link HandlerAdapter} return type.
+ * Message handler adapter implementing this interface can detect {@link HandlerAdapter} async return types.
  *
  * @author Wang zhiyang
+ *
  * @since 3.2
  */
 public interface AsyncRepliesAware {
 
 	/**
-	 * Return true if this listener is request/reply and the replies are async.
+	 * Return true if the {@link HandlerAdapter} return type is async.
 	 * @return true for async replies.
 	 * @since 3.2
 	 */

spring-kafka/src/main/java/org/springframework/kafka/listener/adapter/ContinuationHandlerMethodArgumentResolver.java

@@ -30,7 +30,9 @@
  * but for regular {@link HandlerMethodArgumentResolver} contract.
  *
  * @author Wang Zhiyang
+ *
  * @since 3.2
+ *
  * @see org.springframework.messaging.handler.annotation.reactive.ContinuationHandlerMethodArgumentResolver
  */
 public class ContinuationHandlerMethodArgumentResolver implements HandlerMethodArgumentResolver {

spring-kafka/src/test/kotlin/org/springframework/kafka/listener/EnableKafkaKotlinCoroutinesTests.kt

@@ -56,7 +56,7 @@ import java.util.concurrent.TimeUnit
 @SpringJUnitConfig
 @DirtiesContext
 @EmbeddedKafka(topics = ["kotlinAsyncTestTopic1", "kotlinAsyncTestTopic2",
-		"kotlinAsyncBatchTestTopic1", "kotlinAsyncBatchTestTopic2", "kotlinReplyTopic1"])
+		"kotlinAsyncBatchTestTopic1", "kotlinAsyncBatchTestTopic2", "kotlinReplyTopic1"], partitions = 1)
 class EnableKafkaKotlinCoroutinesTests {
 
 	@Autowired