upgrade java to 21 (#972)

Author: Taz03

.github/workflows/basic-checks.yml

@@ -3,7 +3,7 @@ name: Basic checks
 on: [pull_request]
 
 env:
-  JAVA_VERSION: 20
+  JAVA_VERSION: 21
 
 jobs:
   spotless:

.github/workflows/code-analysis.yml

@@ -8,7 +8,7 @@ on:
     - cron: '0 20 * * 4'
 
 env:
-  JAVA_VERSION: 20
+  JAVA_VERSION: 21
 
 jobs:
   sonar:

.github/workflows/docker-publish.yaml

@@ -7,7 +7,7 @@ on:
       - 'master'
 
 env:
-  JAVA_VERSION: 20
+  JAVA_VERSION: 21
 
 jobs:
   docker:

.github/workflows/docker-verify.yaml

@@ -3,7 +3,7 @@ name: Docker Verify
 on: [pull_request]
 
 env:
-  JAVA_VERSION: 20
+  JAVA_VERSION: 21
 
 jobs:
   docker:

.github/workflows/releases.yaml

@@ -10,7 +10,7 @@ defaults:
     shell: bash
 
 env:
-  JAVA_VERSION: 20
+  JAVA_VERSION: 21
 
 jobs:
 

README.md

@@ -1,7 +1,7 @@
 # TJ-Bot
 
 [![codefactor](https://img.shields.io/codefactor/grade/github/together-java/tj-bot)](https://www.codefactor.io/repository/github/together-java/tj-bot)
-![Java](https://img.shields.io/badge/Java-20-ff696c)
+![Java](https://img.shields.io/badge/Java-21-ff696c)
 [![license](https://img.shields.io/github/license/Together-Java/TJ-Bot)](https://github.com/Together-Java/TJ-Bot/blob/master/LICENSE)
 ![GitHub release (latest by date)](https://img.shields.io/github/v/release/Together-Java/TJ-Bot?label=release)
 

application/build.gradle

@@ -18,7 +18,7 @@ repositories {
 var outputImage = 'togetherjava.org:5001/togetherjava/tjbot:' + System.getenv('BRANCH_NAME') ?: 'latest'
 
 jib {
-    from.image = 'eclipse-temurin:20'
+    from.image = 'eclipse-temurin:21'
     to {
         image = outputImage
         auth {

build.gradle

@@ -65,8 +65,8 @@ subprojects {
         options.encoding = 'UTF-8'
 
         // Nails the Java-Version of every Subproject
-        sourceCompatibility = JavaVersion.VERSION_20
-        targetCompatibility = JavaVersion.VERSION_20
+        sourceCompatibility = JavaVersion.VERSION_21
+        targetCompatibility = JavaVersion.VERSION_21
     }
 
     compileJava(compileTasks)