[hw-1] implement cart service

cart/internal/domain/model/product.go

@@ -0,0 +1,21 @@
+package model
+
+import (
+	"fmt"
+
+	"route256/cart/internal/domain/entity"
+)
+
+type Product struct {
+	Name  string
+	Price int32
+	Sku   entity.Sku `validate:"gt=0"`
+}
+
+func (p *Product) Validate() error {
+	if err := validate.Struct(p); err != nil {
+		return fmt.Errorf("invalid requested values: %w", err)
+	}
+
+	return nil
+}