Feat(medusa, medusa-js, medusa-react): Include sales channels in related queries as an optional expand parameter (#1816)

**What**
- Add `transformQuery` to get endpoints for product, order and cart
  - ensure that the default relations (when getting a singular entity) includes sales channels when enabled
- Add `EmptyQueryParams` class in common types to prevent query parameters while using `transformQuery`
- update product-, order- and cartFactory to include sales channels if provided
- remove `packages/medusa/src/controllers/products/admin-list-products.ts`

**Testing** 
- expands sales channel for single order
- expands sales channels for orders with expand parameter 
- returns single product with sales channel 
- expands sales channels for products with expand parameter
- returns cart with sales channel for single cart

Fixes CORE-293

Co-authored-by: Sebastian Rindom <7554214+srindom@users.noreply.github.com>
Co-authored-by: Adrien de Peretti <25098370+adrien2p@users.noreply.github.com>

packages/medusa/src/models/product.ts

@@ -9,7 +9,6 @@ import {
   ManyToMany,
   ManyToOne,
   OneToMany,
-  OneToOne,
 } from "typeorm"
 import { DbAwareColumn } from "../utils/db-aware-column"
 import { Image } from "./image"
@@ -21,10 +20,7 @@ import { ProductVariant } from "./product-variant"
 import { ShippingProfile } from "./shipping-profile"
 import { SoftDeletableEntity } from "../interfaces/models/soft-deletable-entity"
 import { generateEntityId } from "../utils/generate-entity-id"
-import {
-  FeatureFlagColumn,
-  FeatureFlagDecorators,
-} from "../utils/feature-flag-decorators"
+import { FeatureFlagDecorators } from "../utils/feature-flag-decorators"
 import { SalesChannel } from "./sales-channel"
 
 export enum ProductStatus {