flatamount, the total values in the receivers array must equal the total invoice amount.
percentage, the total values in the receivers array must equal 100%.
fee_bearerof the invoice is
account, you can specify who bearers the fees in the split transaction. You can either spread the transaction fees across the receivers or choose a single receiver to bear the fees. When the selected receivers settlement value is less than the fees, we would automatically spread fees across all receivers.