Merge pull request #28572 from overleaf/kh-analytics-for-custom-checkout

[web] add `payment-page-view`, `payment-page-toggle-payment`, `payment-page-toggle-country` events to Stripe custom checkout

GitOrigin-RevId: a576ee706909e1e363e9ca256e2303a8fd9e1aa7

services/web/types/subscription/subscription-creation-preview.ts

@@ -7,6 +7,8 @@ export type SubscriptionCreationPreview = {
   taxRate: number
   billingCycleInterval: 'month' | 'year'
   coupon: PaymentProviderCoupon
+  priceId: string
+  lookupKey: string
   trialLength: number | null
   plan: Plan
 }