correct javadoc

Author: ankit--sethi

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/security/authc/apikey/CustomTokenAuthenticator.java

@@ -15,9 +15,9 @@
 import org.elasticsearch.xpack.core.security.authc.AuthenticationToken;
 
 /**
- * An extension point to provide a custom API key authenticator implementation.
+ * An extension point to provide a custom token authenticator implementation. For example, a custom API key or a custom OAuth2 token implementation.
  * The implementation is wrapped by a core `Authenticator` class and included in the authenticator chain _before_ the
- * default API key authenticator.
+ * respective "standard" authenticator(s).
  */
 public interface CustomTokenAuthenticator {
 

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/AbstractPluggableAuthenticator.java

@@ -1,3 +1,10 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
 package org.elasticsearch.xpack.security.authc;
 
 import org.elasticsearch.action.ActionListener;

x-pack/plugin/security/src/main/java/org/elasticsearch/xpack/security/authc/PluggableOAuth2TokenAuthenticator.java

@@ -1,8 +1,20 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
 package org.elasticsearch.xpack.security.authc;
 
 import org.elasticsearch.xpack.core.security.authc.AuthenticationToken;
 import org.elasticsearch.xpack.core.security.authc.apikey.CustomTokenAuthenticator;
 
+/**
+ * An adapter for {@link CustomTokenAuthenticator} that implements the {@link Authenticator} interface, so the custom API key authenticator
+ * can be plugged into the authenticator chain. Module dependencies prevent us from introducing a direct extension point for
+ * an {@link Authenticator}.
+ */
 public class PluggableOAuth2TokenAuthenticator extends AbstractPluggableAuthenticator {
 
     private CustomTokenAuthenticator customOAuth2TokenAuthenticator;