CI: add JDK 21 (LTS) to testing matrix. (#599)

Author: rhusar

.github/workflows/ci.yml

@@ -70,3 +70,19 @@ jobs:
           cache: maven
       - name: Build with Maven
         run: mvn --batch-mode --no-transfer-progress clean verify
+
+  arquillian-build-jdk21:
+    name: Integration - JDK 21
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - name: Build with Maven
+        uses: actions/checkout@v4
+      - name: Setup JDK 21
+        uses: actions/setup-java@v4
+        with:
+          java-version: 21
+          distribution: temurin
+          cache: maven
+      - name: Build with Maven
+        run: mvn --batch-mode --no-transfer-progress clean verify