feat(membership): pay through stripe checkout, adding apple pay and google pay

TODO.md

@@ -12,12 +12,18 @@ Remove items from this list once they are done.
   `android.enableMinifyInReleaseBuilds: false` in the `expo-build-properties` plugin config in
   `app.json`): smaller APK, but native Android stack traces get obfuscated unless the R8 mapping
   file reaches Bugsink, which doesn't document ProGuard/R8 mapping support. Also check whether
-  Stripe or Sentry need ProGuard keep rules
-- verify the SDK 58 upgrade on devices: `useFrameworks: "dynamic"` (needed since
-  `@stripe/stripe-react-native` 0.78 pulls the Stripe iOS SDK through Swift Package Manager) is
-  untested with Skia, Reanimated and Sentry, so do an iOS EAS build first; then a test-mode
-  purchase on Android and iOS including a card that requires authentication (exercises the
-  `handleURLCallback` deep link), an expiry reminder notification, and an error that lands in Bugsink
+  Sentry needs ProGuard keep rules
+- verify the SDK 58 upgrade on devices: an expiry reminder notification and an error that lands
+  in Bugsink, on Android and an iOS EAS build
+- verify the Stripe Checkout purchase flow end to end (needs galtinn deployed with
+  `/api/stripe/checkout-session/app/` first): a test-mode purchase on Android and iOS with `4242…`,
+  a card that requires 3D Secure and a cancel, checking the app lands back on the proof with the
+  right toast. Check Apple Pay shows inside the iOS auth session (ASWebAuthenticationSession); if
+  not, switch to `WebBrowser.openBrowserAsync` plus a `Linking` listener. Confirm Google Pay with
+  a real card in Google Wallet, and that Apple Pay, Google Pay and Link are enabled in the Stripe
+  Dashboard's Checkout settings
+- once app versions using the Payment Sheet are gone, drop galtinn's `/api/stripe/payment-sheet/`
+  endpoint and its `payment_intent.succeeded` handling
 - test in ios emulator? (`npm run ios`, requires macOS)
 - characters in the password input field are invisible
 - ask for date of birth and place of study when registering: galtinn now requires them on its web
@@ -32,14 +38,3 @@ Remove items from this list once they are done.
   - try [`@expo/ui`](https://docs.expo.dev/versions/latest/sdk/ui/), production-ready as of SDK 56:
     real SwiftUI / Jetpack Compose components that could back the homegrown ones in
     `src/components/`
-- add [Apple Pay](https://docs.stripe.com/apple-pay?platform=react-native) for membership
-  payments: either natively in the payment sheet (register the merchant ID
-  `merchant.no.neuf.chateau` + Apple Pay certificate, set `merchantIdentifier` in the
-  `@stripe/stripe-react-native` plugin config, pass `applePay` to `initPaymentSheet`,
-  new iOS build), or for free by moving payment to a Stripe-hosted Checkout page in the
-  browser (needs a backend Checkout Session endpoint and a return deep link)
-- add [Google Pay](https://docs.stripe.com/google-pay?platform=react-native) for
-  membership payments: either natively in the payment sheet (`enableGooglePay: true` in
-  the plugin config, pass `googlePay` to `initPaymentSheet`, request production access in
-  the Google Pay & Wallet Console, new Android build), or for free via the same
-  Stripe-hosted Checkout page as for Apple Pay