- Check base class, all checks derive from it and have a common calling
convention.
- Add retries.
- Add a DNS zone transfer check. Turns out if fails on ns1. WIP.
- A wrapper around checking web sites. Just provide a list of URLs.

Outbound traffic on port 25 is restricted by AWS. Removing the
restriction will raise the cost of the project.

The bucket already has the environment in it.

Ease debugging.

There's a limit of 5 targets per rule. So rule per function it is.

The triggers will be created last (after the rule, the functions and the
aliases are created). Without them, there won't be any invocations and
obviously the alarms will trigger.

Monitor the monitoring system.

Start at the basics, DNS.

Plus subscriptions and IAM policy to publish messages.