Completes the registration of a new passkey and returns the stored Passkey.
The challenge ID returned by `passkey.startRegistration()`.
The credential created by the platform's passkey API, serialized in the W3C `RegistrationResponseJSON` format.
final Passkey passkey = await supabase.auth.passkey.verifyRegistration(
challengeId: registration.challengeId,
credential: credential,
);