Require Java 21 or newer (#781)

Author: uhafner

pom.xml

@@ -66,7 +66,7 @@
   </distributionManagement>
 
   <properties>
-    <maven.compiler.release>17</maven.compiler.release>
+    <maven.compiler.release>21</maven.compiler.release>
     <maven.compiler.testRelease>${maven.compiler.release}</maven.compiler.testRelease>
     <!-- Generate metadata for reflection on method parameters -->
     <maven.compiler.parameters>true</maven.compiler.parameters>