Bump JDK from 17 to 21

Change-Id: I11939b6e3f628531799e69d9815705e7c8234741
diff --git a/.github/workflows/ci_test.yml b/.github/workflows/ci_test.yml
index 4899835..448709c 100644
--- a/.github/workflows/ci_test.yml
+++ b/.github/workflows/ci_test.yml
@@ -29,11 +29,11 @@
           repository: KorAP/Koral
           path: Koral
 
-      - name: Set up JDK 17
+      - name: Set up JDK 21
         uses: actions/setup-java@v4
         with:
           distribution: 'temurin'
-          java-version: 17
+          java-version: 21
 
       - name: Build and install Krill
         run: mvn --file Krill/pom.xml install
diff --git a/README.md b/README.md
index 7f50d22..3aaf3e8 100644
--- a/README.md
+++ b/README.md
@@ -22,7 +22,7 @@
 # Setup
 
 
-#### Prerequisites: Jdk 17, Git, Maven 3
+#### Prerequisites: Jdk 21, Git, Maven 3
 
 Clone the latest version of Kustvakt
 ```
diff --git a/pom.xml b/pom.xml
index fdec52f..b8cdf93 100644
--- a/pom.xml
+++ b/pom.xml
@@ -6,7 +6,7 @@
 	<artifactId>Kustvakt</artifactId>
 	<version>0.80-SNAPSHOT</version>
 	<properties>
-		<java.version>17</java.version>
+		<java.version>21</java.version>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
 		<jersey.version>3.1.11</jersey.version>
 		<hibernate.version>7.1.3.Final</hibernate.version>
@@ -200,7 +200,6 @@
 				<artifactId>maven-compiler-plugin</artifactId>
 				<version>3.14.1</version>
 				<configuration>
-					<compilerVersion>${java.version}</compilerVersion>
 					<source>${java.version}</source>
 					<target>${java.version}</target>
 					<!-- <compilerArguments> <processor>lombok.launch.AnnotationProcessorHider$AnnotationProcessor</processor>