LRU cache for TOI response #37
Description
Summary
If we could cache which addresses and transactions the toi have responded as banned we would be able to refuse any tx with these addresses or transactions without asking the toi service again.
This would be even more useful in the event of a downtime (or any other problem) of the toi service, we could still safely refuse transactions based on previous responses from the toi.
A problem with this approach is that the api used does not indicate which addresses/transactions were banned, only that there were at least 1 banned address or transaction on the list passed to the api.
To make a LRU cache possible we would need to change this behavior on the api or implement another api for this (i.e. once the existence of the banned resource is confirmed, ask another api to see which one).