Deprecate auto-configuration for RestHighLevelClient

Closes gh-28598

Author: wilkinsona

spring-boot-project/spring-boot-actuator/src/main/java/org/springframework/boot/actuate/elasticsearch/ElasticsearchRestHealthIndicator.java

@@ -49,7 +49,14 @@ public class ElasticsearchRestHealthIndicator extends AbstractHealthIndicator {
 
 	private final JsonParser jsonParser;
 
-	@SuppressWarnings("deprecation")
+	/**
+	 * Create a new {@code ElasticsearchRestHealthIndicator} using the {@link RestClient}
+	 * obtained from the given high-level client.
+	 * @param client the high-level client
+	 * @deprecated since 2.7.0 for removal in 2.9.0 in favor of
+	 * {@link #ElasticsearchRestHealthIndicator(RestClient)}
+	 */
+	@Deprecated
 	public ElasticsearchRestHealthIndicator(org.elasticsearch.client.RestHighLevelClient client) {
 		this(client.getLowLevelClient());
 	}

spring-boot-project/spring-boot-docs/src/docs/asciidoc/data/nosql.adoc

@@ -270,7 +270,8 @@ You can use `spring.elasticsearch.*` properties to further tune how the clients
 [[data.nosql.elasticsearch.connecting-using-rest.restclient]]
 ===== Connecting to Elasticsearch using RestClient
 If you have `elasticsearch-rest-client` on the classpath, Spring Boot will auto-configure and register a `RestClient` bean.
-If you have `elasticsearch-rest-high-level-client` on the classpath a `RestHighLevelClient` bean will be registered as well.
+If you have `elasticsearch-rest-high-level-client` on the classpath a `RestHighLevelClient` bean will be auto-configured as well.
+Following Elasticsearch's deprecation of `RestHighLevelClient`, its auto-configuration is deprecated and will be removed in a future release.
 In addition to the properties described previously, to fine-tune the `RestClient` and `RestHighLevelClient`, you can register an arbitrary number of beans that implement `RestClientBuilderCustomizer` for more advanced customizations.
 To take full control over the clients' configuration, define a `RestClientBuilder` bean.