ci: PLT-632: Failed build notification

Author: nikitabelonogov

.github/workflows/build.yml

@@ -13,6 +13,7 @@ env:
   DOCKER_BUILD_CONFIG_BRANCH: "master"
   DOCKER_BUILD_CONFIG_PATH: ".github/docker-build-config.yml"
   DOCKER_EXAMPLES_DIRECTORY: "label_studio_ml/examples"
+  SLACK_NOTIFICATION_CHANNEL_ID: "CKL2D6D2P"
 
 jobs:
   build-image:
@@ -151,3 +152,24 @@ jobs:
             const docker_build_config = yaml.load(docker_build_config_content);
             
             core.setOutput("matrix-include", docker_build_config);
+
+  notification:
+    name: "Send Slack Notification"
+    if: failure()
+    runs-on: ubuntu-latest
+    needs:
+      - build-image
+    steps:
+      - name: Send Slack Notification
+        if: always()
+        uses: slackapi/[email protected]
+        env:
+          WORKFLOW: "<https://github.com/${{ github.repository }}/actions/runs/${{ github.run_id }}|workflow>"
+        with:
+          method: chat.postMessage
+          token: ${{ secrets.SLACK_LSE_BOT_TOKEN }}
+          payload: |
+            channel: "${{ env.SLACK_NOTIFICATION_CHANNEL_ID }}"
+            text: >+
+              :x: Build workflow failed
+              [ ${{ env.WORKFLOW }} ]