Idea: use BOLT12 Withdraw Offers to clear outlays

[farscapian]

Currently, payouts only succeed (and outlays go down) when the member node is online AND when when the node receives a income event on an offer. This feature #94 suggests that we can make it such that the member node only needs to be online to receive payment since payouts occur regularly and on a recurring basis.

A third model would be to employ withdraw offers. Say every two days we check member outlays and issue BOLT12 withdraw offers representing the current member outlay. If the destination is an npub (see #105), then we can encrypt that new withdrawal offer to the npub and send it as either a DM or a replaceable event to the npubs preferred relays (see NIP-05). Withdrawal offers are issued ONLY AFTER any existing offers for the member have expired.

Nostr clients knowing the associated nsec can then decrypt the DM and execute the withdrawal offer to reduce the outlay by the amount specified in the withdrawal offer. Note, any outlays accrued AFTER the withdrawal offer is issued WILL NOT clear.