refactor(LOY-62): implement code review feedback

utils/membershipLevels.ts

@@ -0,0 +1,5 @@
+import { MembershipLevelEnum } from "@/constants/membershipLevels"
+
+export function isMembershipLevel(value: string): value is MembershipLevelEnum {
+  return Object.values(MembershipLevelEnum).some((level) => level === value)
+}

utils/rewards.ts

@@ -1,6 +1,11 @@
-import { RESTAURANT_REWARD_IDS, REWARD_IDS } from "@/constants/rewards"
+import {
+  COUPON_REWARD_TYPES,
+  RESTAURANT_REWARD_IDS,
+  REWARD_IDS,
+} from "@/constants/rewards"
 
 import type {
+  CouponRewardType,
   RestaurantRewardId,
   RewardId,
 } from "@/types/components/myPages/rewards"
@@ -40,3 +45,9 @@ export function isRestaurantOnSiteTierReward(
 ): boolean {
   return isOnSiteTierReward(reward) && isRestaurantReward(reward.reward_id)
 }
+
+export function isCouponRewardType(
+  type: RewardWithRedeem["rewardType"]
+): type is CouponRewardType {
+  return COUPON_REWARD_TYPES.some((t) => t === type)
+}