feat(ci): add GitHub Actions workflow for Docker builds

Author: EnricoBausenhart

.github/workflows/build_docker.yml

@@ -0,0 +1,69 @@
+name: Build Docker Images
+
+on:
+  push:
+
+jobs:
+  test:
+    name: Run Java Tests
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - uses: actions/setup-java@v4
+        with:
+          java-version: "21"
+          distribution: "temurin"
+
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v4
+
+      - name: Build with Gradle
+        run: cd server && ./gradlew build
+
+  build:
+    name: Build and Push Docker Images
+    needs: test
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Log in to the Container registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+        with:
+          platforms: all
+
+      - name: Install Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ghcr.io/${{ github.repository }}
+          tags: |
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=ref,event=branch
+            type=ref,event=pr
+
+      - name: Build and push Docker Images
+        uses: docker/build-push-action@v5
+        with:
+          platforms: linux/amd64,linux/arm64
+          context: .
+          file: deployment/compose.yml
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}