Apply suggestions from code review

Co-authored-by: Yoann Rodière <[email protected]>

extensions/elasticsearch-rest-client/runtime/src/main/java/io/quarkus/elasticsearch/restclient/lowlevel/runtime/ElasticsearchConfig.java

@@ -26,13 +26,13 @@ public class ElasticsearchConfig {
     public String protocol;
 
     /**
-     * The username used for authentication.
+     * The username for basic HTTP authentication.
      */
     @ConfigItem
     public Optional<String> username;
 
     /**
-     * The password used for authentication.
+     * The password for basic HTTP authentication.
      */
     @ConfigItem
     public Optional<String> password;
@@ -52,6 +52,9 @@ public class ElasticsearchConfig {
     /**
      * The number of IO thread.
      * By default, this is the number of locally detected processors.
+     * <p>
+     * Thread counts higher than the number of processors should not be necessary because the I/O threads rely on non-blocking operations,
+     * but you may want to use a thread count lower than the number of processors.
      *
      * @see <a href="https://www.elastic.co/guide/en/elasticsearch/client/java-rest/current/_number_of_threads.html">number of
      *      threads</a>