Decouple per_hour from hour increments

[zanebclark]

Define per_hour to support different units of time

In the current Rate spec, the "rate" part of the Rate object (per_hour) is defined as an integer. If a municipality were to define rates by day, the conversion of such a rate to an hourly rate would yield a float (e.g. $100 / day = $4.16666666667 / hour). For measurements smaller than an hour, there's no potential that scaling the rate would result in a float. A per-minute integer rate (e.g. 6 cents per minute) converted to a per-hour rate would continue to be an integer (360 cents per hour), as multiplying an integer by an integer yields an integer. The same logic applies to second and sub-second rates. Still, an additional step would be required to convert CDS-served policies (360 cents per hour) back to the original rate definition (6 cents per minute).

Proposal: Define the "rate" part of the Rate object with rate and rate_unit instead of per_hour.

Name	Type	Required/Optional	Description
per_hour	Integer	Required	The rate per hour for this space in cents (or the smallest denomination of local currency).
rate	Integer	Required	The rate for this space in cents (or the smallest denomination of local currency) per rate_unit.
rate_unit	String	Required	The unit of time associated with the rate. One of "second", "minute", "hour", "day".
increment_minutes	Integer	Optional	If specified, this is the smallest amount of time a user can pay for (e.g., if increment_minutes is 15, a user can pay for 15, 30, 45, etc. minutes).
increment_amount	Integer	Optional	If specified, the rate for this space is rounded up to the nearest increment of this amount, specified in the same units as rate.
start_minutes	Integer	Optional	The amount of time the vehicle must have already been present in the Curb Zone before this rate starts applying. If not specified, this rate starts when the vehicle arrives.
end_minutes	Integer	Optional	The amount of time after which the rate stops applying. If not specified, this rate ends when the vehicle departs.

Some example Rates:

2 cents per second

{
  "rate": 2,
  "rate_unit": "second"
}

$100 per day

{
  "rate": 10000,
  "rate_unit": "day"
}

30 cents per 15 minute interval

{
  "rate": 2,
  "rate_unit": "minute",
  "increment_minutes": 15
}

[schnuerle]

Agree with this change. And it's like we do it in Rules in MDS. Updated to your suggestion here.

[zanebclark]

Splendid. Thanks!