add ResponseException#status

this allows accessing the HTTP status code of the response when an API
returns a `ResponseException`. this was not possible through
`getResponse` since `Response` itself is package-private and thus its
members (even though they are marked as `public`) are not accessible to
external consumers.

as there's no test coverage for `ResponseException` i haven't added any
for the new API either, as it is a trivial API and it was unclear how
adding test coverage for it would fit into the existing test coverage.

solves #749

Signed-off-by: Ralph Ursprung <Ralph.Ursprung@avaloq.com>

java-client/src/main/java/org/opensearch/client/transport/httpclient5/ResponseException.java

@@ -64,7 +64,7 @@ static String buildMessage(Response response) throws IOException {
             response.getRequestLine().getMethod(),
             response.getHost(),
             response.getRequestLine().getUri(),
-            response.getStatusLine().toString()
+            response.getStatusLine()
         );
 
         if (response.hasWarnings()) {
@@ -73,7 +73,7 @@ static String buildMessage(Response response) throws IOException {
 
         HttpEntity entity = response.getEntity();
         if (entity != null) {
-            if (entity.isRepeatable() == false) {
+            if (!entity.isRepeatable()) {
                 entity = new BufferedHttpEntity(entity);
                 response.getHttpResponse().setEntity(entity);
             }
@@ -92,4 +92,12 @@ static String buildMessage(Response response) throws IOException {
     public Response getResponse() {
         return response;
     }
+
+    /**
+     * Status code returned by Elasticsearch. Shortcut for
+     * {@code response().status()}.
+     */
+    public int status() {
+        return this.response.getStatusLine().getStatusCode();
+    }
 }