Af.3 - On-chain recurrent payments

Subscriptions without a middleman. The sender funds a smart contract, the receiver redeems what is due on a schedule (monthly, for example), and the sender can reclaim whatever has not yet been paid out. It is best modeled as a vesting-style contract, without the time-lock or hash secret of a swap contract. A foundation for subscriptions and for “staking for a service”.