🔧 Backport build-tag github workflow from develop

.github/workflows/build-tag.yml

@@ -21,6 +21,22 @@ jobs:
     with:
       gh_ref: ${{ github.ref_name }}
 
+  notify:
+    name: Notifications
+    runs-on: ubuntu-24.04
+    needs: build-docker
+
+    steps:
+      - name: Notify Mattermost
+        uses: mattermost/action-mattermost-notify@master
+        with:
+          MATTERMOST_WEBHOOK_URL: ${{ secrets.MATTERMOST_WEBHOOK }}
+          MATTERMOST_CHANNEL: bot-alerts-cicd
+          TEXT: |
+            🐳 *[PENPOT] Docker image available.*
+            🔗 Run: https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}
+            @infra
+
   publish-final-tag:
     if: ${{ !contains(github.ref_name, '-RC') && !contains(github.ref_name, '-alpha') && !contains(github.ref_name, '-beta')  && contains(github.ref_name, '.') }}
     needs: build-docker