CI: add a workflow for deploying an preview app to Azure

.github/workflows/azure-webapps-python.yml

@@ -0,0 +1,71 @@
+name: Build and deploy Python app to Azure Web App
+
+env:
+  AZURE_WEBAPP_NAME: st-undp
+  PYTHON_VERSION: '3.11'
+
+on:
+  push:
+    branches: [ "main" ]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Set up Python version
+        uses: actions/setup-python@v4
+        with:
+          python-version: ${{ env.PYTHON_VERSION }}
+          cache: 'pip'
+
+      - name: Install Poetry
+        run: |
+          curl -sSL https://install.python-poetry.org | python3 -
+          echo "$HOME/.local/bin" >> $GITHUB_PATH
+
+      - name: Install dependencies
+        run: |
+          poetry config virtualenvs.create false
+          poetry install
+
+      - name: Export requirements.txt
+        run: |
+          poetry export -f requirements.txt -o requirements.txt --without-hashes
+
+      - name: Building web app
+        uses: azure/appservice-build@v2
+
+      - name: Upload artifact for deployment
+        uses: actions/upload-artifact@v3
+        with:
+          name: python-app
+          path: |
+            .
+            !venv/  # Exclude the virtual environment if it exists
+  
+  deploy:
+    permissions:
+      contents: none
+    runs-on: ubuntu-latest
+    needs: build
+
+    steps:
+      - name: Download artifact from build job
+        uses: actions/download-artifact@v3
+        with:
+          name: python-app
+          path: .
+
+      - name: 'Deploy to Azure Web App'
+        id: deploy-to-webapp
+        uses: azure/webapps-deploy@v3
+        with:
+          app-name: ${{ env.AZURE_WEBAPP_NAME }}
+          publish-profile: ${{ secrets.AZURE_WEBAPP_PUBLISH_PROFILE }}