Refactor: update Stripe subscription model decorator to use subscription model methods directly

[jonwaldstein]

Resolves #

Description

This pull request includes changes to the SubscriptionModelDecorator class and its related tests to simplify the code and improve maintainability. The most important changes include the removal of unused imports, updating methods to use model methods, and refactoring the test cases.

Code simplification and maintainability improvements:

• src/PaymentGateways/Gateways/Stripe/StripePaymentElementGateway/Webhooks/Decorators/SubscriptionModelDecorator.php: Removed unused imports to clean up the code.
• src/PaymentGateways/Gateways/Stripe/StripePaymentElementGateway/Webhooks/Decorators/SubscriptionModelDecorator.php: Updated shouldEndSubscription, shouldCreateRenewal, and handleRenewal methods to use model methods for better encapsulation and maintainability.
• tests/Feature/Gateways/Stripe/StripePaymentElement/Webhooks/Listeners/InvoicePaymentSucceededTest.php: Refactored the testShouldCompleteSubscription method to remove unnecessary caching of donations.
• tests/Feature/Gateways/Stripe/StripePaymentElement/Webhooks/Listeners/InvoicePaymentSucceededTest.php: Updated assertions to use the totalDonations method for clarity and accuracy.

Affects

The logic for handling the Stripe subscription webhook listener InvoicePaymentSucceeded

• shouldCreateRenewal
• handleRenewal
• shouldEndSubscription

Visuals

N/A

Testing Instructions

QA

• Setup Stripe webhooks and create subscription
• Trigger webhook event to create renewal (InvoicePaymentSucceeded)

Pre-review Checklist

• Acceptance criteria satisfied and marked in related issue
• Relevant @unreleased tags included in DocBlocks
• Includes unit tests
• Reviewed by the designer (if follows a design)
• Self Review of code and UX completed

[glaubersilva]

@jonwaldstein It makes me wonder... In Stripe, is it possible for a renewal to have a different value from the subscription? In which scenarios it can happen?

[jonwaldstein]

@glaubersilva that's a great question! Ideally there should not be a different value from the subscription in Give. My train of thought here was to use Stripe as the source of truth in case there is a different value - so we are recording the actual paid amount. The 2 scenarios where this would be possible (yet, very unlikely) are:

1. The subscription was somehow updated in Stripe and not in Give
2. The amount was recorded wrong in Give