Handling date and times as object classes

[cdmwebs]

The API expects dates and times to be serialized.

def datetime_as_object(datetime)
  {
    __class__: "datetime",
    iso_string: datetime.utc.iso8601
  }
end

def date_as_object(date)
  {
    __class__: "date",
    iso_string: date.iso8601
  }
end

Let's add this to the request/response handler so we don't have to deal with this in application code.