Add slack notification for failed deployments

.github/workflows/cd.yml

@@ -87,3 +87,16 @@ jobs:
         with:
           run: ${{ steps.apply-run.outputs.run_id }}
           comment: "Apply Run from GitHub Actions CI ${{ github.sha }}"
+      - name: Report Status
+        if: failure()
+        uses: rtCamp/action-slack-notify@v2
+        env:
+          SLACK_WEBHOOK: ${{ secrets.SLACK_WEBHOOK_URL }}
+          SLACK_USERNAME: "GitHub Actions"
+          SLACK_COLOR: "#ff0000"
+          MSG_MINIMAL: "ref,actions url"
+          SLACK_TITLE: "Deployment Failed"
+          SLACK_MESSAGE: "Automatic deployment to ${{ env.TF_WORKSPACE }} failed"
+        with:
+          status: ${{ job.status }}
+          notify_when: "failure"