Add withPassword(String) method to secure Elasticsearch

Instead of providing env settings manually, we can simplify the usage of Elasticsearch in the context of TestContainers by just asking a password.
Behind the scene, we do provide the needed env settings.

docs/modules/elasticsearch.md

@@ -38,12 +38,11 @@ or set `client.transport.ignore_cluster_name` to `true`.
 ## Secure your Elasticsearch cluster
 
 The default distribution of Elasticsearch comes with the basic license which contains security feature.
-You can turn on security by providing some extra environment settings:
+You can turn on security by providing a password:
 
 ```java
 ElasticsearchContainer container = new ElasticsearchContainer("docker.elastic.co/elasticsearch/elasticsearch:7.5.2")
-    .withEnv("ELASTIC_PASSWORD", "changeme")
-    .withEnv("xpack.security.enabled", "true");
+    .withPassword("changeme");
 ```
 
 In which case you can create the Client like this:

modules/elasticsearch/src/main/java/org/testcontainers/elasticsearch/ElasticsearchContainer.java

@@ -56,6 +56,12 @@ public ElasticsearchContainer(String dockerImageName) {
             .withStartupTimeout(Duration.ofMinutes(2)));
     }
 
+    public ElasticsearchContainer withPassword(String password) {
+        withEnv("ELASTIC_PASSWORD", password);
+        withEnv("xpack.security.enabled", "true");
+        return this;
+    }
+
     public String getHttpHostAddress() {
         return getContainerIpAddress() + ":" + getMappedPort(ELASTICSEARCH_DEFAULT_PORT);
     }

modules/elasticsearch/src/test/java/org/testcontainers/elasticsearch/ElasticsearchContainerTest.java

@@ -79,10 +79,7 @@ public void elasticsearchDefaultTest() throws IOException {
 
     @Test
     public void elasticsearchSecuredTest() throws IOException {
-        try (ElasticsearchContainer container = new ElasticsearchContainer()
-            .withEnv("ELASTIC_PASSWORD", ELASTICSEARCH_PASSWORD)
-            .withEnv("xpack.security.enabled", "true")
-        ) {
+        try (ElasticsearchContainer container = new ElasticsearchContainer().withPassword(ELASTICSEARCH_PASSWORD)) {
             container.start();
 
             // The cluster should be secured so it must fail when we try to access / without credentials