feat: Line Items API Routes (#6478)

**What**
- `POST /store/carts/:id/line-items`
- `POST /store/carts/:id/line-items/:id`
- `DELETE /store/carts/:id/line-items/:id`

**Outstanding**
- Integration tests
- Module integrations: Payment, Fulfillment, Promotions

Depends on #6475 and #6449.

packages/types/src/cart/common.ts

@@ -400,6 +400,10 @@ export interface CartLineItemDTO extends CartLineItemTotalsDTO {
    * When the line item was updated.
    */
   updated_at?: Date
+  /**
+   * When the line item was deleted.
+   */
+  deleted_at?: Date
 }
 
 export interface CartDTO {

packages/types/src/cart/mutations.ts

@@ -189,6 +189,7 @@ export interface UpdateLineItemDTO
   title?: string
   quantity?: number
   unit_price?: number
+  metadata?: Record<string, unknown> | null
 
   tax_lines?: UpdateTaxLineDTO[] | CreateTaxLineDTO[]
   adjustments?: UpdateAdjustmentDTO[] | CreateAdjustmentDTO[]

packages/types/src/cart/workflows.ts

@@ -1,4 +1,5 @@
-import { CartDTO } from "./common"
+import { CartDTO, CartLineItemDTO } from "./common"
+import { UpdateLineItemDTO } from "./mutations"
 
 export interface CreateCartCreateLineItemDTO {
   quantity: number
@@ -32,6 +33,12 @@ export interface CreateCartCreateLineItemDTO {
   metadata?: Record<string, unknown>
 }
 
+export interface UpdateLineItemInCartWorkflowInputDTO {
+  cart: CartDTO
+  item: CartLineItemDTO
+  update: Partial<UpdateLineItemDTO>
+}
+
 export interface CreateCartAddressDTO {
   first_name?: string
   last_name?: string