This is a small lambda handler that emits a metric to cloudwatch whenever there
are avaialable book based on desiredDays configureed in lambda-handler.py.
You can set this up to run on AWS lambda and trigger it via a cloudwatch event
rule cron expression. The lambda role has to have ses:SendEmail
permissions to notify.
This should all be within the free tier for AWS for SES and Lambda.
TODO: handle session and actually book parking.