(BE-58,,59): extend db schema & build stock transfer api

- Extend DB schema for stock transfers
- Build stock transfer API (create,)

internal/entities/stock_transfer_delivery_item.go

@@ -0,0 +1,12 @@
+package entities
+
+// PIVOT TABLE TRANSFER
+type StockTransferDeliveryItem struct {
+	Id                      uint64 `gorm:"primaryKey;autoIncrement"`
+	StockTransferDeliveryId uint64
+	StockTransferDetailId   uint64
+	Quantity                float64
+	// Relations
+	StockTransferDelivery *StockTransferDelivery `gorm:"foreignKey:StockTransferDeliveryId"`
+	StockTransferDetail   *StockTransferDetail   `gorm:"foreignKey:StockTransferDetailId"`
+}