Merge branch '2-deklaration-der-ziel-jvm-version' into 'main'

Resolve "Deklaration der Ziel JVM Version"

See merge request !26

pom.xml

@@ -11,7 +11,7 @@
 
     <properties>
         <java.version>11</java.version>
-        <maven.compiler.release>${java.version}</maven.compiler.release>
+        <maven.compiler.release>11</maven.compiler.release>
 
         <encoding>UTF-8</encoding>
         <project.build.sourceEncoding>${encoding}</project.build.sourceEncoding>