[hw-1] implement cart service

cart/internal/app/server/server.go

@@ -0,0 +1,25 @@
+package server
+
+import (
+	"context"
+
+	"route256/cart/internal/domain/entity"
+	"route256/cart/internal/domain/model"
+)
+
+type CartService interface {
+	AddItem(ctx context.Context, userID entity.UID, item *model.Item) error
+	GetItemsByUserID(ctx context.Context, userID entity.UID) (*model.Cart, error)
+	DeleteItem(ctx context.Context, userID entity.UID, sku entity.Sku) error
+	DeleteItemsByUserID(ctx context.Context, userID entity.UID) error
+}
+
+type Server struct {
+	cartService CartService
+}
+
+func NewServer(cartService CartService) *Server {
+	return &Server{
+		cartService: cartService,
+	}
+}