Uptime Monitoring

[bohdan-shulha]

We need to add basic uptime monitoring so that users (e.g. us) would not need to use extra 3rd-party services to track if their websites are up and running. Moreover, this will allow us to easily combine deployment status with uptime dashboards.

For the first iteration, we wouldn't need any status pages or multi-region support (yet it has to be pre-architectured).

Users should be able to:

1. Configure basic HTTP checks: request URL, response HTTP status, some keyword(s), the frequency, number of failed requests to trigger the alert, and the number of successful requests to resolve an alert.
2. See the data on a dashboard of the specific check.
3. Recieve alerts on their E-Mails (team e-mails? team owner's e-mail? a new "notifications" team's email?).