Upgrade CI build from Java 17 to 21

Co-authored-by: vorburger <298598+vorburger@users.noreply.github.com>

Author: Copilot

.github/workflows/maven.yml

@@ -24,10 +24,10 @@ jobs:
 
     steps:
       - uses: actions/checkout@v6
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v5
         with:
-          java-version: "17"
+          java-version: "21"
           distribution: "temurin"
           cache: maven
       - name: Build with Maven

pom.xml

@@ -17,8 +17,8 @@
 
   <properties>
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-    <maven.compiler.source>17</maven.compiler.source>
-    <maven.compiler.target>17</maven.compiler.target>
+    <maven.compiler.source>21</maven.compiler.source>
+    <maven.compiler.target>21</maven.compiler.target>
   </properties>
 
   <dependencies>
@@ -94,7 +94,7 @@
         <artifactId>maven-compiler-plugin</artifactId>
         <version>3.14.1</version>
         <configuration>
-          <release>17</release>
+          <release>21</release>
           <source>${maven.compiler.source}</source>
           <target>${maven.compiler.target}</target>
           <encoding>UTF-8</encoding>