ci: notify Slack when the deploy workflow is finished

.github/workflows/deploy.yml

@@ -52,3 +52,28 @@ jobs:
         run: pip install -r requirements/base.txt
       - name: Deploy environment
         run: tc-admin apply --environment ${{matrix.environment}}
+
+  notify:
+    if: github.event_name == 'push'
+    runs-on: ubuntu-latest
+    needs: [check, apply]
+    strategy:
+      matrix:
+        environment: ["staging", "firefoxci"]
+    steps:
+      - name: Notify Slack
+        if: always()
+        run: |
+          WORKFLOW_URL="https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}"
+          SLACK_MESSAGE="*${{ github.workflow }} ${{ github.repository }}* (<${WORKFLOW_URL}|View Workflow>)"
+
+          for JOB_NAME in ${!needs.*.result}; do
+            JOB_STATUS="${{ needs[$JOB_NAME].result }}"
+            if [ $"JOB_STATUS" == "success" ]; then
+              SLACK_MESSAGE="${SLACK_MESSAGE}\n:white_check_mark: *${JOB_NAME}*
+            else
+              SLACK_MESSAGE="${SLACK_MESSAGE}\n:x: *${JOB_NAME}*
+            fi
+          done
+
+          curl -X POST -H 'Content-type: application/json' --data "{\"text\":\"${SLACK_MESSAGE}\"}" ${{ secrets.SLACK_WEBHOOK_URL }}