a better backend deployment workflow

.gitea/workflows/backend_build-deploy-stg.yaml

@@ -0,0 +1,25 @@
+on:
+  pull_request:
+    branches:
+      - main
+    paths:
+      - backend/**
+
+name: Build and deploy the backend to staging
+
+jobs:
+  build-and-push:
+    name: Build and push image
+    uses: ./workflow_build-image.yaml
+    with:
+      tag: unstable
+    secrets:
+      PACKAGE_REGISTRY_ACCESS: ${{ secrets.PACKAGE_REGISTRY_ACCESS }}
+  
+  deploy-prod:
+    name: Deploy to production
+    uses: ./workflow_deploy-container.yaml
+    with:
+      environment: stg
+    secrets:
+      PACKAGE_REGISTRY_ACCESS: ${{ secrets.KUBE_CONFIG }}