docs: upgrades to Java 21 (#14)

* chore: upgrades gitlab steps to use Java 21

* docs: upgrade to Java 21

* chore: upgrade gradle project version sourceCompatibility -> Java 21

Author: hartmut-co-uk

.github/template/README.md

@@ -10,7 +10,7 @@ Automated migration completed, enjoy the template.
 
 ## Features
 - 🥷 One-click **automated initial project migration workflow** (GitHub Action)
-- **Java 17** (corretto) 🤝 **Gradle Kotlin DSL**, version catalog
+- **Java 21** (corretto) 🤝 **Gradle Kotlin DSL**, version catalog
 - **GitHub Actions CI/CD pipeline**, 👷 efficient build pipeline, caching, integration tests, test report & failed test annotations
 - 🚀 **One-click release** process + **publish** to **Maven Central**
 - **Security & 🚦 Vulnerability scan** with **[trivy](https://github.com/aquasecurity/trivy)** & GitHub CodeQL Analysis

.github/workflows/callable.build.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'corretto'
-          java-version: '17'
+          java-version: '21'
       - uses: gradle/wrapper-validation-action@v1
       - name: Setup Gradle
         uses: gradle/[email protected]

.github/workflows/callable.code-analysis.codeql.yml

@@ -38,7 +38,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'corretto'
-          java-version: '17'
+          java-version: '21'
       - uses: gradle/wrapper-validation-action@v1
       - name: Setup Gradle
         uses: gradle/[email protected]

.github/workflows/callable.code-analysis.trivy.yml

@@ -20,7 +20,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'corretto'
-          java-version: '17'
+          java-version: '21'
       - uses: gradle/wrapper-validation-action@v1
       - name: Setup Gradle
         uses: gradle/[email protected]

.github/workflows/callable.gradle-release.yml

@@ -30,7 +30,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'corretto'
-          java-version: '17'
+          java-version: '21'
       - uses: gradle/wrapper-validation-action@v1
       - name: Setup Gradle
         uses: gradle/[email protected]

.github/workflows/callable.integration-test.yml

@@ -14,7 +14,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'corretto'
-          java-version: '17'
+          java-version: '21'
       - uses: gradle/wrapper-validation-action@v1
       - name: Setup Gradle
         uses: gradle/[email protected]

.github/workflows/callable.publish-javadoc.yml

@@ -17,7 +17,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'corretto'
-          java-version: '17'
+          java-version: '21'
       - uses: gradle/wrapper-validation-action@v1
       - name: Setup Gradle
         uses: gradle/[email protected]

.github/workflows/callable.publish-sonatype.yml

@@ -13,7 +13,7 @@ jobs:
       - uses: actions/setup-java@v3
         with:
           distribution: 'corretto'
-          java-version: '17'
+          java-version: '21'
       - uses: gradle/wrapper-validation-action@v1
       - name: Setup Gradle
         uses: gradle/[email protected]

.java-version

@@ -1 +1 @@
-17
+21

README.md

@@ -11,7 +11,7 @@ _TLDR:_ Java Library GitHub Template Repository
 
 ## Features
 - 🥷 One-click **automated initial project migration workflow** (GitHub Action)
-- **Java 17** (corretto) 🤝 **Gradle Kotlin DSL**, version catalog
+- **Java 21** (corretto) 🤝 **Gradle Kotlin DSL**, version catalog
 - **GitHub Actions CI/CD pipeline**, 👷 efficient build pipeline, caching, integration tests, test report & failed test annotations
 - 🚀 **One-click release** process + **publish** to **Maven Central**
 - **Security & 🚦 Vulnerability scan** with **[trivy](https://github.com/aquasecurity/trivy)** & GitHub CodeQL Analysis