feat(types,utils): add promotions create with application method (#5945)

What:

- Promotions can be created with its bare attributes
- Promotions one to one relationship with ApplicationMethod can be created with its attributes + validation

RESOLVES CORE-1592
RESOLVES CORE-1595

packages/promotion/integration-tests/__fixtures__/promotion/data.ts

@@ -0,0 +1,14 @@
+import { PromotionType } from "@medusajs/utils"
+
+export const defaultPromotionsData = [
+  {
+    id: "promotion-id-1",
+    code: "PROMOTION_1",
+    type: PromotionType.STANDARD,
+  },
+  {
+    id: "promotion-id-2",
+    code: "PROMOTION_2",
+    type: PromotionType.STANDARD,
+  },
+]

packages/promotion/integration-tests/__fixtures__/promotion/index.ts

@@ -0,0 +1,22 @@
+import { SqlEntityManager } from "@mikro-orm/postgresql"
+import { Promotion } from "@models"
+import { defaultPromotionsData } from "./data"
+
+export * from "./data"
+
+export async function createPromotions(
+  manager: SqlEntityManager,
+  promotionsData = defaultPromotionsData
+): Promise<Promotion[]> {
+  const promotion: Promotion[] = []
+
+  for (let promotionData of promotionsData) {
+    let promotion = manager.create(Promotion, promotionData)
+
+    manager.persist(promotion)
+
+    await manager.flush()
+  }
+
+  return promotion
+}