Remove deprecated RN accelerated checkout customer shape

[kieran-osgood-shopify]

What?

In v3 we deprecated the customer constructor that allows both access token and email and phone but we released this under a non-breaking change so that we didn't have to bump React by a major and instead we added a development warning to indicate to users that this would become a failure in v4. This PR just implements that.

Why?

We configure this as an error to avoid the footgun for users of combining the state.
This will show up as a typescript error

The RN v4 API should only expose the two supported customer identification modes: Customer Account access token, or contact fields

Using both is illegal as it introduces an impossible state of the customer being populated from both, and encourages footgun with expectations of fallbacks or combinations of the state.

How to test

• shadowenv exec --dir /Users/ko/.claudex/worktrees/Shopify@checkout-kit/cx-remove-deprecated-rn-context -- /opt/dev/bin/dev rn api dump
• shadowenv exec --dir /Users/ko/.claudex/worktrees/Shopify@checkout-kit/cx-remove-deprecated-rn-context -- /opt/dev/bin/dev rn api check
• shadowenv exec --dir /Users/ko/.claudex/worktrees/Shopify@checkout-kit/cx-remove-deprecated-rn-context -- /opt/dev/bin/dev rn lint module
• shadowenv exec --dir /Users/ko/.claudex/worktrees/Shopify@checkout-kit/cx-remove-deprecated-rn-context -- /opt/dev/bin/dev rn lint sample
• shadowenv exec --dir /Users/ko/.claudex/worktrees/Shopify@checkout-kit/cx-remove-deprecated-rn-context -- /opt/dev/bin/dev rn test js
• shadowenv exec --dir /Users/ko/.claudex/worktrees/Shopify@checkout-kit/cx-remove-deprecated-rn-context -- /opt/dev/bin/dev rn test ios

[kieran-osgood-shopify]

• Remove deprecated RN accelerated checkout customer shape #262 👈 (View in Graphite)
• main

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[github-actions]

React Native — Coverage Report

Lines	Statements	Branches	Functions
	91.66% (319/348)	87.86% (181/206)	100% (82/82)

[markmur]

Can't we harden this?

Suggested change

	export type AcceleratedCheckoutCustomer =
	| {accessToken: string; email?: never; phoneNumber?: never}
	| {accessToken?: never; email: string; phoneNumber: string};
	export type AcceleratedCheckoutCustomer =
	| {accessToken: string}
	| {email: string; phoneNumber: string};

[kieran-osgood-shopify]

I believe with the union you suggest it softens the enforcements due to structural sharing, at least thats what I was attempting to enforce here

export type FlexibleCustomer =
| {accessToken: string;}
| {email: string; phoneNumber: string};

const customer: FlexibleCustomer = {
  //  ^ this doesn't reject due to structural sharing
  accessToken: 'token',
  email: 'test@example.com',
  phoneNumber: '+123',
};

export type StrictCustomer =
| {accessToken: string; email?: never; phoneNumber?: never}
| {accessToken?: never; email: string; phoneNumber: string};

const strict_customer: StrictCustomer = {
  //  ^ correctly rejects
  accessToken: 'token',
  email: 'test@example.com',
  phoneNumber: '+123',
};