rangeMarginRaw method
see yobi for same function with several stores
Implementation
num rangeMarginRaw(DateTime firstDate, DateTime lastDate) =>
    sumTicketTypePerRange(
      TicketType.sell,
      start: firstDate,
      end: lastDate,
    ) +
    sumTicketTypePerRange(
      TicketType.spend,
      start: firstDate,
      end: lastDate,
    ) -
    sumTicketTypePerRange(
      TicketType.wage,
      start: firstDate,
      end: lastDate,
    );