Handle failed code flow updates

[premun]

Context

When an uncaught exception happens in the PR updater processing code flows, we would like to learn about it.
Example: We try to trigger a code flow subscription and there's some kind of a problem and we are not even able to create a PR branch because of a conflict. We need to get some sort of an alert.

Goal

Figure out how to report a failure (GH issue opened? Or just an error in the service and have alerting in place?).