Install Gradle on CI server

.github/workflows/pr-validate.yml

@@ -21,22 +21,14 @@ jobs:
           java-version: '17'
           distribution: 'temurin'
 
-      - name: Grant execute permission for gradlew
-        run: chmod +x backend/gradlew
-
-      - name: Cache Gradle packages
-        uses: actions/cache@v4
+      - name: Set up Gradle
+        uses: gradle/actions/setup-gradle@v4
         with:
-          path: |
-            ~/.gradle/caches
-            ~/.gradle/wrapper
-          key: ${{ runner.os }}-gradle-${{ hashFiles('**/*.gradle*', '**/gradle-wrapper.properties') }}
-          restore-keys: |
-            ${{ runner.os }}-gradle-
+          gradle-version: '8.6'
 
       - name: Run backend tests
         working-directory: backend
-        run: ./gradlew test --no-daemon
+        run: gradle test --no-daemon
 
   unit-test-frontend:
     name: Frontend Unit Tests