Persist user carts in database

prisma/schema.prisma

@@ -70,6 +70,7 @@ model User {
   sentInvitations      Invitation[]           @relation("InvitationManager")
   acceptedInvitations  Invitation[]           @relation("InvitationAcceptor")
   messengerConnections MessengerConnection[]
+  cart                 Cart?
   clientOrders         Order[]                @relation("OrderClient")
   managerOrders        Order[]                @relation("OrderManager")
   orderStatusEvents    OrderStatusEvent[]
@@ -91,6 +92,7 @@ model DeliveryAddress {
   unrestrictedValue String?
   fiasId            String?
   defaultForUsers   User[]   @relation("UserDefaultDeliveryAddress")
+  carts             Cart[]
   orders            Order[]
   createdAt         DateTime @default(now())
   updatedAt         DateTime @updatedAt
@@ -179,11 +181,43 @@ model Product {
   isCustomizable  Boolean       @default(false)
   isActive        Boolean       @default(true)
   inventory       ProductStock[]
+  cartItems       CartItem[]
   orderItems      OrderItem[]
   createdAt       DateTime      @default(now())
   updatedAt       DateTime      @updatedAt
 }
 
+model Cart {
+  id                String           @id @default(cuid())
+  userId            String           @unique
+  user              User             @relation(fields: [userId], references: [id], onDelete: Cascade)
+  deliveryAddressId String?
+  deliveryAddress   DeliveryAddress? @relation(fields: [deliveryAddressId], references: [id], onDelete: SetNull)
+  items             CartItem[]
+  createdAt         DateTime         @default(now())
+  updatedAt         DateTime         @updatedAt
+
+  @@index([deliveryAddressId])
+}
+
+model CartItem {
+  id             String   @id @default(cuid())
+  cartId         String
+  cart           Cart     @relation(fields: [cartId], references: [id], onDelete: Cascade)
+  productId      String
+  product        Product  @relation(fields: [productId], references: [id], onDelete: Cascade)
+  productName    String
+  sku            String
+  isCustomizable Boolean  @default(false)
+  quantity       Decimal  @db.Decimal(14, 3)
+  parameters     Json
+  createdAt      DateTime @default(now())
+  updatedAt      DateTime @updatedAt
+
+  @@unique([cartId, productId])
+  @@index([productId])
+}
+
 model Warehouse {
   id        String        @id @default(cuid())
   code      String        @unique