fun stats(period: String?, cashRegisterName: String?): CategoriesStatsInfo?
Returns stats by categories.
period - filters by date period
cashRegisterName - filters by cash register name
com.srv4pos.server.api.exceptions.TypeMismatchJsonException - if period java.lang.String isn't convertible to
java.util.Date.
Return
com.srv4pos.server.api.category.CategoriesStatsInfo with stats.