The big breaking change for our code (not mentioned in the changelog) is
that the built-in validator for the `date-time` format now requires the
`rfc3339-validator` package instead of the `strict-rfc3339` package.
This updates the requirements file to use `rfc3339-validator`. Without
this change, wrong `date-time` formats would always silently pass validation.
* Added unit tests for the get_complaint_count endpoint
* Updated the schema to use 'date' format instead of 'datetime'
* Updated the complaint endpoint to convert start_date and end_date to
be dates instead of strings
