Add new TierOption Messaging (Address comments)- 4

[SabrinaTardio]

Task/Issue URL: https://app.asana.com/1/137249556945/project/1204186595873227/task/1212208990048369?focus=true

Description Addresses comment on the previous PRs

Testing Steps

1. Smoke test purchase flow as is (for both app Store and stripe)
2. Turn the “tierMessagingEnabled” feature flag on
3. In the subscription debug menu and in Custom base subscription URL use https://eponomareva.duckduckgo.com/subscriptions
4. In the subscription debug menu make sure you are using the staging endpoint
5. You should now test the landing page and doing a purchase for both AppStore and Stripe
6. Everything should work as normal

Note: For Stripe you need to have VPN on a US server

Impact and Risks

What could go wrong?

Quality Considerations

Notes to Reviewer

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Internal references:

Definition of Done | Engineering Expectations | Tech Design Template

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Note

Introduce SubscriptionTier and TierFeature types, replace EntitlementPayload across APIs and flows, update caches/managers, fix Stripe region to "us", and migrate tests accordingly.

• Subscription Models & API:
  • Replace EntitlementPayload with TierFeature in GetSubscriptionTierFeaturesResponse, TierProduct.entitlements, and related APIs.
  • Introduce top-level SubscriptionTier (replacing SubscriptionTierOptions.Tier) and update SubscriptionTierOptions accordingly.
  • Update SubscriptionFeatureMappingCacheV2 to return [String: [TierFeature]] and adjust fallback mapping.
• Flows & Managers:
  • Update StorePurchaseManagerV2 and StripePurchaseFlowV2 to build tiers using SubscriptionTier and TierFeature.
  • In Stripe flow, always send region parameter as "us" and remove region detection helper.
• Auth Token:
  • Minor cleanup in EntitlementPayload (remove explicit init) while retaining structure for JWT parsing.
• Tests & Mocks:
  • Migrate all tests and test utilities to TierFeature/SubscriptionTier types and updated endpoints/mocks.

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