Migrations shouldn't fail RuboCop checks - especially lint checks, such
as the nested method check. To avoid changing code in existing
migrations, add the magic comment to the top of each of them to skip
that file.
1) Adds a DB migration for all services to toggle on push, issue, and merge events.
2) Upon an issue or merge request event, fire service hooks.
3) Slack service supports custom messages for each of these events. Other services
not supported at the moment.
4) Label merge request hooks with their corresponding actions.
