Tag on-call on Slack about failed e2e (#340)

Author: nikita-vanyasin

.github/workflows/e2e.yaml

@@ -251,6 +251,8 @@ jobs:
           token: ${{ secrets.GITHUB_TOKEN }}
           status: 'failure'
           notification_title: "E2E tests failed for {branch}"
+          mention_groups: "S099W77RQ7J" # @on-call-terraform-provider
+          mention_groups_when: "failure"
           footer: "{run_url}"
         env:
           SLACK_WEBHOOK_URL: ${{ secrets.SLACK_WEBHOOK }}