Integrate GitLab Alerts

GitLab has a monitoring tool for alerts. The backend could send alerts whenever, e.g., a webhook endpoint fails, an InternalServerError is thrown, etc.

Integration is very simple:

• Create a library for alerts. It's main function is format the alert and call the HTTP endpoint exposed by GitLab
• Look for critical places we would like to create an alert and call the library

We can also set the end_time of the alert, meaning that an alert is not only a precise point in time, but rather a problem that might be solved, and therefore the alert is obsolete. I'm not sure we would have a use case like this, but it's good to keep in mind if ever we need it.