GH-8692 Add createIndexes to MongoDbMessageStore

Fixes https://github.com/spring-projects/spring-integration/issues/8692

* Added `createIndexes` in `AbstractConfigurableMongoDbMessageStore`
* Added Javadoc for `setCreateIndex()` method
* Removed `afterPropertiesSet()` in `MongoDbChannelMessageStore` and update `whats-new.adoc` and `mongodb.adoc` files

**Cherry-pick to `6.1.x` & `6.0.x`**

spring-integration-mongodb/src/test/java/org/springframework/integration/mongodb/store/ConfigurableMongoDbMessageGroupStoreTests.java

@@ -16,6 +16,7 @@
 
 package org.springframework.integration.mongodb.store;
 
+import java.util.List;
 import java.util.Map;
 
 import org.bson.Document;
@@ -25,6 +26,8 @@ import org.junit.jupiter.api.Test;
 import org.springframework.context.support.ClassPathXmlApplicationContext;
 import org.springframework.core.convert.converter.Converter;
 import org.springframework.data.convert.ReadingConverter;
+import org.springframework.data.mongodb.core.MongoTemplate;
+import org.springframework.data.mongodb.core.index.IndexInfo;
 import org.springframework.integration.IntegrationMessageHeaderAccessor;
 import org.springframework.integration.channel.PriorityChannel;
 import org.springframework.integration.channel.QueueChannel;
@@ -42,6 +45,7 @@ import static org.assertj.core.api.Assertions.assertThat;
  * @author Amol Nayak
  * @author Artem Bilan
  * @author Artem Vozhdayenko
+ * @author Adama Sorho
  *
  */
 class ConfigurableMongoDbMessageGroupStoreTests extends AbstractMongoDbMessageGroupStoreTests {
@@ -134,6 +138,12 @@ class ConfigurableMongoDbMessageGroupStoreTests extends AbstractMongoDbMessageGr
 						.getClass());
 		context.refresh();
 
+		List<IndexInfo> indexesInfo =
+				new MongoTemplate(MONGO_DATABASE_FACTORY)
+						.indexOps("customConverterCollection")
+						.getIndexInfo();
+		assertThat(indexesInfo).hasSize(0);
+
 		TestGateway gateway = context.getBean(TestGateway.class);
 		String result = gateway.service("foo");
 		assertThat(result).isEqualTo("FOO");

spring-integration-mongodb/src/test/java/org/springframework/integration/mongodb/store/ConfigurableMongoDbMessageStore-CustomConverter.xml

@@ -29,6 +29,8 @@
 
 	<beans:bean id="messageStore" parent="abstractMessageStore">
 		<beans:constructor-arg name="mappingMongoConverter" ref="customConverter"/>
+		<beans:constructor-arg name="collectionName" value="customConverterCollection"/>
+		<beans:property name="createIndexes" value="false" />
 	</beans:bean>
 
 	<gateway id="gateway"