Implements Closeable for SDKClients

Signed-off-by: Owais Kazi <owaiskazi19@gmail.com>

src/main/java/org/opensearch/sdk/SDKClient.java

@@ -9,6 +9,7 @@
 
 package org.opensearch.sdk;
 
+import java.io.Closeable;
 import java.io.IOException;
 
 import com.fasterxml.jackson.annotation.JsonTypeInfo;
@@ -39,7 +40,7 @@
 /**
  * This class creates SDKClient for an extension to make requests to OpenSearch
  */
-public class SDKClient {
+public class SDKClient implements Closeable {
     private OpenSearchClient javaClient;
     private RestClient restClient;
     private RestHighLevelClient highLevelClient;
@@ -98,11 +99,13 @@ public OpenSearchClient initializeJavaClient(String hostAddress, int port) {
     }
 
     /**
+     * @deprecated Provided for compatibility with existing plugins to permit migration. New development should not use this client
      * Creates High Level Rest Client for SDK.
      * @param hostAddress The address of OpenSearch cluster, client can connect to
      * @param port The port of OpenSearch cluster
      * @return The SDKClient implementation of RestHighLevelClient. The user is responsible for calling {@link #doCloseHighLevelClient()} when finished with the client
      */
+    @Deprecated
     public RestHighLevelClient initializeRestClient(String hostAddress, int port) {
         RestClientBuilder builder = builder(hostAddress, port);
 
@@ -131,4 +134,10 @@ public void doCloseHighLevelClient() throws IOException {
             highLevelClient.close();
         }
     }
+
+    @Override
+    public void close() throws IOException {
+        doCloseJavaClient();
+        doCloseHighLevelClient();
+    }
 }