Spam detection, automatic banning & monitoring[REQUEST]

[goodc0re]

It would be useful to have a way to monitor our relays for spam, as well as some configurable options to automatically ban nPubs from posting via our relays that have been detected to send out a large amount of messages and / or duplicate messages.

Automation is needed imho since there are already automated tools out there to send out spam. Spammers will be able to generate unlimited fresh nPubs to use for spamming, so a manual review and banning option will likely not be good enough.