first try for backend workflow on pull requests

.github/workflows/pr.yml

@@ -0,0 +1,28 @@
+name: Lokaler Merge Workflow
+
+on:
+  push:
+    paths:
+      - 'backend/**'
+  pull_request:
+    types: [opened, reopened]
+
+jobs:
+  merge_locally:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Merge PR into target branch locally
+        run: git merge ${{ github.head_ref }}
+
+      - name: Set up JDK 17
+        uses: actions/setup-java@v3
+        with:
+          java-version: '17'
+          distribution: 'temurin'
+
+      - name: Run local tests
+        run: mvn --batch-mode --update-snapshots --no-transfer-progress -f backend/pom.xml verify