Notify SCA BE team on Slack when scheduled pipeline that republishes analyzer images fails

Notify the groupcomposition analysis backend team when a scheduled pipeline that republishes the Docker images of an analyzer they maintain fails.

Scheduled pipelines that republish the Docker images of Dependency Scanning and License Scanning analyzers were introduced in https://gitlab.com/gitlab-org/gitlab/-/issues/338826.

create a Slack app for the GitLab workspace. The application will require approval by an admin.
when it's created, enable incoming webhooks for this app
ask access request for Request for Installing a New Webhook (there will be a button on the Incoming Webhook setting page, also ask in it-help for help in slack).
when approved, you get Webhook URL
for each analyzer update the Slack Notifications Settings
- Settings > Integrations > Slack Notifications
- set integration to active
- enable trigger to "notify only on broken pipelines" and set the branch for "Branches for which notifications are to be sent" to Default branch
- set webhook to one set above
test by breaking pipeline run on default branch

Edited Jun 13, 2022 by Oscar Tovar