add gateway (#187)

* feature: add gateway

.github/workflows/docker-image-gateway.yml

@@ -0,0 +1,30 @@
+name: Gateway Docker Image CI
+
+on:
+  push:
+    branches: [ "main" ]
+    paths:
+      - 'backend/**'
+      - 'scripts/images/gateway/**'
+      - '.github/workflows/docker-image-gateway.yml'
+      - '.github/workflows/docker-images-reusable.yml'
+  pull_request:
+    branches: [ "main" ]
+    paths:
+      - 'backend/**'
+      - 'scripts/images/gateway/**'
+      - '.github/workflows/docker-image-gateway.yml'
+      - '.github/workflows/docker-images-reusable.yml'
+  workflow_dispatch:
+  workflow_call:
+
+jobs:
+  call-docker-build:
+    name: Build and Push Gateway Docker Image
+    uses: ./.github/workflows/docker-images-reusable.yml
+    permissions:
+      contents: read
+      packages: write
+    with:
+      service_name: gateway
+      build_dir: .