Feature: add renewal methods to subscription model

[jonwaldstein]

Description

This adds some quality of life methods to subscription model including:

• createRenewal
• shouldCreateRenewal
• shouldEndSubscription

The goal is to unify the way we are dealing with renewals across our gateways.

I noticed throughout different gateways, we are duplicating a lot of the same logic for handling the renewals and are not consistent with the properties being used in the creation of the donation model. For example, sometimes we use the donor's first name vs the initial donation's billing first name, the billing address is not often accounted for, various properties are missing, etc.. With a unified api we can be consistent with the renewal values and which properties are being carried over from the subscription, initial donation, donor, invoice, etc.

This was largely inspired by a SubscriptionModelDecorator I created for Stripe webhooks which is being used in production.

There is also the webhook event handlers that @glaubersilva made that could make use of these methods directly.

Affects

This only introduces new logic to the subscription model and repositories, however will affect gateways in the future as they adopt these methods.

Visuals

N/A

Testing Instructions

• Programmatically test the methods

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

[JasonTheAdams]

This is such a great addition, @jonwaldstein! Great call! 🎉