switch to Java 21

Author: eivanov89

Diff for: pom.xml

@@ -12,9 +12,9 @@
 
     <properties>
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-        <java.version>17</java.version>
-        <maven.compiler.source>17</maven.compiler.source>
-        <maven.compiler.target>17</maven.compiler.target>
+        <java.version>21</java.version>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
         <buildDirectory>${project.basedir}/target</buildDirectory>
         <!--
             Provids a way to limit which assembly package formats we produce.