feat(reports): inventory valuation report.

feat(reports): sales by items report.
feat(reports): purchases by items report.

server/src/interfaces/SalesByItemsSheet.ts

@@ -0,0 +1,43 @@
+import {
+  INumberFormatQuery,
+} from './FinancialStatements';
+
+export interface ISalesByItemsReportQuery {
+  fromDate: Date | string;
+  toDate: Date | string;
+  numberFormat: INumberFormatQuery;
+  noneTransactions: boolean;  
+};
+
+export interface ISalesByItemsSheetMeta {
+  organizationName: string,
+  baseCurrency: string,
+};
+
+export interface ISalesByItemsItem {
+  id: number,
+  name: string,
+  code: string,
+  quantitySold: number,
+  soldCost: number,
+  averageSellPrice: number,
+
+  quantitySoldFormatted: string,
+  soldCostFormatted: string,
+  averageSellPriceFormatted: string,
+  currencyCode: string,
+};
+
+export interface ISalesByItemsTotal {
+  quantitySold: number,
+  soldCost: number,
+  quantitySoldFormatted: string,
+  soldCostFormatted: string,
+  currencyCode: string,
+};
+
+export interface ISalesByItemsSheetStatement {
+  items: ISalesByItemsItem[],
+  total: ISalesByItemsTotal
+};
+