fix: Graph fetch relations with sales & purchases models.

feat: Inventory tracker algorithm lots with FIFO or LIFO cost method.

server/src/interfaces/InventoryTransaction.ts

@@ -0,0 +1,23 @@
+
+
+export interface IInventoryTransaction {
+  id?: number,
+  date: Date,
+  direction: string,
+  itemId: number,
+  quantity: number,
+  rate: number,
+  transactionType: string,
+  transactionId: string,
+};
+
+export interface IInventoryLotCost {
+  id?: number,
+  date: Date,
+  direction: string,
+  itemId: number,
+  rate: number,
+  remaining: number,
+  transactionType: string,
+  transactionId: string,
+}