feat: API key sales channel link (#6851)

What
- Add link between API key and sales channels
- Add API route for batch adding sales channels to a publishable API key
- Clean up API key API routes responses
- Move API key test suite from `integration-tests/modules` to `integration-tests/api`

packages/api-key/src/models/api-key.ts

@@ -6,10 +6,10 @@ import {
 import {
   BeforeCreate,
   Entity,
+  Enum,
   OnInit,
   PrimaryKey,
   Property,
-  Enum,
 } from "@mikro-orm/core"
 
 const TypeIndex = createPsqlIndexStatementHelper({