Add checkTrialOrIntroDiscountEligibility(package: Package)

[fire-at-will]

Motivation

I was creating a mini-paywall in the Settings screen of one of my apps, when I realized that we don't have a function to check the trial/intro eligibility on a single package like we do for a single product. This means that if you only want to check the eligibility of one package, you need to wrap it in an array and then parse it out of a response dictionary, or check the eligibility of the package's product.

This isn't a super ergonomic way to check the eligibility of just one package, and we already have functions to check the eligibility of one StoreProduct, so I created this PR to add a new function to check the trial/intro eligibility of just one package.

Description

Adds the following new APIs to PurchasesType:

@objc(checkTrialOrIntroDiscountEligibilityForPackage:completion:)
func checkTrialOrIntroDiscountEligibility(
   package: Package, 
   completion: @escaping (RevenueCat.IntroEligibilityStatus) -> Void)

func checkTrialOrIntroDiscountEligibility(
   package: Package
) async -> RevenueCat.IntroEligibilityStatus

It also adds unit/API/integration tests for the new functions

---

Note

Low Risk
Additive public API with no change to eligibility logic; behavior matches the existing product-based checks via package.storeProduct.

Overview
Adds checkTrialOrIntroDiscountEligibility(package:) in completion and async forms on Purchases / PurchasesType, mirroring the existing single-StoreProduct APIs so callers can check intro/trial eligibility for one offering package without wrapping it in an array or using package.storeProduct directly.

Implementation delegates to the same trialOrIntroPriceEligibilityChecker path as the product overloads (package.storeProduct). ObjC entry point is checkTrialOrIntroDiscountEligibilityForPackage:completion:; public swiftinterface files are updated accordingly.

Coverage includes unit tests (completion + async), a StoreKit integration test, API testers (Swift + ObjC), and MockPurchases stubs.

^{Reviewed by Cursor Bugbot for commit 68c75d7. Bugbot is set up for automated code reviews on this repo. Configure here.}

[emerge-tools]

📸 Snapshot Test

1 modified, 858 unchanged

Name	Added	Removed	Modified	Renamed	Unchanged	Errored	Approval
PaywallsTester V1 swift-snapshot-testing com.revenuecat.PaywallsTester.v1-snapshots	0	0	1	0	64	0	⏳ Needs approval
RevenueCat com.revenuecat.PaywallsTester	0	0	0	0	274	0	N/A
Paywall Rendering Validation (mac-catalyst-optimized-for-mac) com.revenuecat.paywall-rendering-validation.mac-catalyst-optimized-for-mac	0	0	0	0	130	0	N/A
Paywall Rendering Validation (mac-native) com.revenuecat.paywall-rendering-validation.mac-native	0	0	0	0	130	0	N/A
Paywall Rendering Validation (mac-catalyst-scaled-to-match-ipad) com.revenuecat.paywall-rendering-validation.mac-catalyst-scaled-to-match-ipad	0	0	0	0	130	0	N/A
Paywall Rendering Validation (ios) com.revenuecat.paywall-rendering-validation.ios	0	0	0	0	130	0	N/A

---

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[ajpallares]

Nice addition indeed! Some minor comments, no blockers! Thanks for adding this! 🙌

[ajpallares]

Probably not for this PR, but now that we're adding the singular package: overload to PurchasesType, I realized that the plural checkTrialOrIntroDiscountEligibility(packages:) still lives only on the concrete Purchases class and not in the protocol. I don't think there's a reason for that? Might be worth a follow-up to add it here for consistency (I'd be fine with sneaking it in with this PR though).

[ajpallares]

Related to my previous point, in "Related symbols" we could add the checkTrialOrIntroDiscountEligibility(packages:) method. Conversely, it'd be nice to add a back-reference to package: from the existing product:/productIdentifiers: doc comments

[ajpallares]

Suggested change

	* [iOS Introductory Offers](https://docs.revenuecat.com/docs/ios-subscription-offers).
	* [iOS Introductory Offers](https://docs.revenuecat.com/docs/ios-subscription-offers).

[ajpallares]

Suggested change

	* [iOS Introductory Offers](https://docs.revenuecat.com/docs/ios-subscription-offers).
	* [iOS Introductory Offers](https://docs.revenuecat.com/docs/ios-subscription-offers).