Consider time-in-force orders with deposit/bounty eviction schema

[alnoki]

To enable automatic cancellation or expiry of orders, a time-in-force (TIF) functionality is proposed:

• A maker indicates the time for which their order should be valid.
• Once the time has passed, the matching engine will not match the order.

Note that this presents a potential denial-of-service (DoS) vector: if an actor places excessive TIF orders on a book, then the book may end up with orders that all need to be vacated. This could be prevented by charing a bounty for clearing out vacated orders, which must be paid by TIF order submitters when they submit an order.

[alnoki]

To prevent the DoS vector, TIF orders could require a deposit in either APT (gas coin) or the base asset for the market.

For example the deposit could be the min size for the market in the base asset.

Here, if a TIF order goes stale, then the deposit effectively becomes an eviction bounty.

This logic could also apply to orders in the general case, with a default TIF of several weeks, for example, such that stale orders get evicted from the book.