feat(medusa, stock-location, inventory): Allow modules to integrate with core (#2997)

* feat: module shared resources

packages/inventory/src/index.ts

@@ -0,0 +1,19 @@
+import ConnectionLoader from "./loaders/connection"
+import InventoryService from "./services/inventory"
+import * as InventoryModels from "./models"
+import * as SchemaMigration from "./migrations/schema-migrations/1665748086258-inventory_setup"
+import { ModuleExports } from "@medusajs/medusa"
+
+const service = InventoryService
+const migrations = [SchemaMigration]
+const loaders = [ConnectionLoader]
+const models = Object.values(InventoryModels)
+
+const moduleDefinition: ModuleExports = {
+  service,
+  migrations,
+  loaders,
+  models,
+}
+
+export default moduleDefinition