Coupons Payment

If the D-ASA has coupons, it MUST pay due coupons, according to the time events, with the OPTIONAL pay_coupon method.

The D-ASA MUST pay due coupons, once, to the Landers.

The D-ASA MUST NOT pay coupons before coupon due dates.

In the case of an on-chain payment agent, the D-ASA MUST pay the coupons to the Lander Payment Addresses.