setRequiredBillingContactFields
fun setRequiredBillingContactFields(fields: Set<RequiredBillingContactField>?): AirwallexPaymentSession.Builder
Configure which billing fields the new-card UI should collect and the headless checkout should validate. Pass null (the default) to derive from the legacy setRequireBillingInformation / setRequireEmail flags. An empty set hides the entire billing section.
Card payments only. Google Pay billing is configured separately via GooglePayOptions (billingAddressRequired, emailRequired); changes here do not propagate to the Google Pay sheet.