Project upgrade

- upgrade to Java 21;
- upgrade to spring-boot 3.3.2;
- upgrade to springdoc-openapi 2.6.0;
- upgrade to jib 3.4.3;
- upgrade wrapperVersion to 3.3.2 and apache-maven to 3.9.7;
- upgrade to elasticsearch docker image 8.13.4;
- remove comments in html files.

Author: Ivan Franchin

Diff for: .mvn/wrapper/maven-wrapper.jar

@@ -1,2 +1,19 @@
-distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.5/apache-maven-3.9.5-bin.zip
-wrapperUrl=https://repo.maven.apache.org/maven2/org/apache/maven/wrapper/maven-wrapper/3.2.0/maven-wrapper-3.2.0.jar
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+wrapperVersion=3.3.2
+distributionType=only-script
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.9.7/apache-maven-3.9.7-bin.zip

Diff for: .mvn/wrapper/maven-wrapper.properties

@@ -22,7 +22,7 @@ image::documentation/project-diagram.jpeg[]
 
 == Prerequisites
 
-* https://www.oracle.com/java/technologies/downloads/#java17[`Java 17+`]
+* https://www.oracle.com/java/technologies/downloads/#java21[`Java 21+`]
 * https://www.docker.com/[`Docker`]
 
 == Start Environment

Diff for: README.adoc

@@ -1,7 +1,7 @@
 services:
 
   elasticsearch:
-    image: docker.elastic.co/elasticsearch/elasticsearch:8.10.4
+    image: docker.elastic.co/elasticsearch/elasticsearch:8.13.4
     container_name: elasticsearch
     restart: unless-stopped
     ports: