breaking: add support for apple pay line items to payment sheet

[charliecruzan-stripe]

Summary

Adds in support for apple pay line items to payment sheet, and also expands the possible options for apple pay line items to include those introduced in iOS 15

This does include a couple small breaking changes (small meaning easily migrate-able):

• ApplePay.CartSummaryItem: renamed type to isPending. type is a very general field name and doesn't provide a good description of what it's doing. Migration guide included in CHANGELOG. We run the risk of Apple adding another PKPaymentSummaryItemType, but I think that's unlikely (since they seem to be instead transitioning to wholly different item types such as PKDeferredPaymentSummaryItem)
• ApplePay.CartSummaryItem: added a new required paymentType field. In all existing code, merchants should set this to paymentType: 'Immediate' (since we only had support for Immediate up until this PR).

Motivation

closes #964

context: https://paper.dropbox.com/doc/2022-06-01-PaymentSheet-Apple-Pay-Line-Items-Mobile-API-Review--Bj2jImE0_eYxuR0dPw5B__jyAg-kqjRdFlgqiAxQvKUiBFH3

Testing

Added unit tests for all ApplePayUtils functionality

Documentation

Select one:

• I have added relevant documentation for my changes.
• This PR does not result in any developer-facing changes.

[ramont-stripe]

looks good!

[ScreamZ]

Any. way to support EURO currency ? @charliecruzan-stripe

[jgalianoz]

One question, what is the isPending parameter for? @charliecruzan-stripe

[charliecruzan-stripe]

That sets the PKPaymentSummaryItemType to pending if true, or final if false

[ScreamZ]

@charliecruzan-stripe No idea for my question about euro currency ?

[charliecruzan-stripe]

@ScreamZ are you looking to set the currency to euro in payment sheet, or directly in presentApplePay?