fix: prefill APM fields by canonical key and parse E.164 phone numbers

[roshan-gorasia-cko]

Problem

Two issues with initialData prefilling on the APM form.

1. Prefill only matched the payment method's own parameter key. NextSteps looked up initialData[param.key], so the documented initialData.phone_number silently no-op'd whenever a payment method named the field something else (for example customerPhone). In practice a merchant had to discover each payment method's internal parameter names to prefill anything.

2. An E.164 phone string wasn't parsed. A phone_number passed as "+48123123123" went into the national-number input whole, with the dialing code set to the first entry in the available list. That selected the wrong country, left +CC inside the number box, and submitted a malformed value. The +-prefix splitting logic only existed in the phone field's paste/typing handler, so it never ran for seeded state.

Changes

• resolvePrefilledValue (src/apm/utils.ts) resolves a parameter's prefill value: an exact parameter-key match wins, otherwise the canonical key for that parameter's type (email → type email, phone_number → type phone). Canonical keys now work on every payment method, and a specific parameter can still be targeted directly or used to override a canonical value.
• normalizePhoneValue (src/apm/utils.ts) coerces a prefilled phone into the { dialing_code, value } shape the field renders. An E.164 string is split on a longest-prefix match against the available dialing codes (so +1242 beats +1), separators are ignored, and the browser-locale default is used when the country isn't offered. The object form is still accepted, keyed on dialing_code, including the number key the field emits on input.
• InitialData (src/apm/types.ts) types phone_number as string | { dialing_code?, value? } and allows payment-method-specific keys.

Notes

The prefilling docs present email / phone_number as universal keys and document the phone value as a bare E.164 string. Both are now true of the SDK; the docs should be extended to cover the object form and to note that a specific parameter key can also be passed and takes precedence.

Tests

test/apm/prefill.test.ts — 15 cases covering key/type resolution precedence and E.164 splitting. yarn test, yarn build and yarn lint all pass.