When a build fails for a commit, create a todo for the author of the
merge request that commit is the HEAD of. If the commit isn't the HEAD
commit of any MR, don't do anything. If there already is a todo for that
user and MR, don't do anything.
Current limitations:
- This isn't configurable by project.
- The author of a merge request might not be the person who pushed the
breaking commit.
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.
Sean McGivern