Optional. When true, this payment method is set as primary for repayment and the primary flag is cleared on the customer's other payment methods of the same type. When false, it is explicitly marked non-primary; siblings are not changed. When omitted or null, the designation is unchanged.

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 false, the funding designation is removed from this method. When omitted or null, the funding designation is unchanged.