chore: refactor dc events payload

[jakubjasinsky]

Summary

Normalize all Dynamic Checkout event payloads to consistently include invoice_id, use snake_case keys, and flatten nested data structures. This ensures consumers receive a uniform event shape regardless of the event type, and adds missing events (tokenize_payment_success) to payment methods that were not dispatching them.

Changes

Event payload normalization (events.ts)

• All dispatch methods now require invoiceId as a parameter and include invoice_id in every event payload
• Renamed payload keys from camelCase to snake_case (invoiceId → invoice_id, returnUrl → return_url)
• Flattened { details: { ... } } wrapping in dispatchPaymentSubmittedEvent, dispatchPaymentCancelledEvent, and dispatchPaymentPendingEvent — data is now passed directly as the event detail
• Added reason field to payment error and pending event payloads
• Added errorData normalization in dispatchPaymentErrorEvent to handle non-object errors (e.g., string) safely before spreading

Tokenize success event coverage

• Added dispatchTokenizePaymentSuccessEvent to card.ts, apm.ts (both regular and save-for-future flows), and saved-apm.ts
• Previously only apple-pay.ts and google-pay.ts dispatched this event

Pending callback signature update (processout.ts)

• Changed makeCardPayment pending callback from (data: any) => void to (resourceId: string, reason: string | null) => void
• Pending callback now passes data?.message as the reason

Native APM improvements (native-apm.ts)

• Added onPaymentSubmit callback, invoked on PAYMENT_INIT, so Dynamic Checkout can dispatch payment_submitted for native APM methods

Apple Pay / Google Pay event fixes

• Fixed dispatchApplePaySessionError which previously created the event but never included the error in the payload
• Wrapped static method references with arrow functions to preserve this context for invoiceId

Example HTML cleanup

• Removed native APM event listeners (no longer needed in the example)
• Updated event names, added missing event listeners, standardized console log format

Impact

• Breaking change for event consumers: All event payloads now use snake_case keys (invoice_id instead of invoiceId). The payment_submitted, payment_cancelled, and payment_pending events no longer nest data under e.detail.details — fields are now directly on e.detail.
• Breaking change for makeCardPayment pending callback: Signature changed from (data) => void to (resourceId, reason) => void.

Testing Plan

• Mount Dynamic Checkout and listen for all events — verify every event includes invoice_id in its payload
• Complete a card payment — verify tokenize_payment_success fires with { token, invoice_id }
• Complete an APM redirect payment — verify tokenize_payment_success fires after redirect
• Complete an APM payment with save-for-future — verify tokenize_payment_success fires
• Complete a saved APM redirect payment — verify tokenize_payment_success fires
• Trigger a payment error — verify payment_error event includes invoice_id and reason
• Trigger a pending payment — verify payment_pending event includes invoice_id, payment_method_name, and reason directly on e.detail (not nested under details)
• Complete Apple Pay / Google Pay flows — verify events include invoice_id
• Test native APM payment — verify payment_submitted event fires on init
• Verify no e.detail.details nesting exists on any event

Additional Context

The previous event system had inconsistent shapes: some events included invoice_id, some didn't; some used camelCase, some snake_case; some wrapped data in { details }, others didn't. This made it difficult for consumers to rely on a consistent contract. This PR establishes a uniform pattern: every event includes invoice_id, all keys are snake_case, and no unnecessary nesting.