Given only a facility id, the default behavior of this endpoint will return relevent rate history details (for ALL units) with an
effective_datetime falling on or between the beginning-of-day and end-of-day on which the request was made.
unit_id may be supplied with the request, limiting the response results to rate history details associated with the given unit.
end_date may be supplied with the request, which can provide rate history details over a span of time vs. the default behavior which is a 1 day timespan. The
end_date may be no more than 31 days from one another.