This endpoint records a new fuel price. Call it once the user has confirmed it: from its startDate on, the
calculated modes of the tables that use this fuel price schedule compute their surcharge from these prices.
Find fuelPriceScheduleId with GET api/v1/fuelsurcharges/fuel-prices. Always send startDate, as yyyy-MM-dd;
only the day is kept. A startDate that already has a price is refused, which also confirms a previous call;
so is a startDate before the first price. Adding the first price of an empty fuel price schedule fails.
Leave currencySymbol empty: it is ignored. The fuel prices cannot be read back or deleted through the API.
On success the response has no body; an unknown fuel price schedule returns a 404. Requires an
administrator; other users get a 403.