Optional. When omitted or null, the new payment method is created without changing primary status on any sibling. When true, this payment method is set as primary and all other payment methods of the same type for this customer have their primary flag cleared. When false, this payment method is explicitly saved as non-primary; siblings are not changed.

Optional. Marks this payment method as the single method the loan is FUNDED (disbursed) to. Independent of isPrimary, which governs repayment - so funding and repayment can point at different methods. When true, this becomes the customer's only funding method and the flag is cleared on all their other methods, across every type. When omitted or null, the funding designation is unchanged. Accepted at the top level or nested under cardDetails/bankDetails.