Handling print statements in chat2 using EDD pattern (specific to waku-rln-relay)

[staheri14]

Problem

Print statements should ideally happen inside the main program, but not from inside other procedures in an ad-hoc manner.
Right now in chat2, this pattern is violated in the publish proc where a warning message is printed on the console when a published message is found spam.
This issue is to address this anti-pattern. Possibly by updating a few function interfaces to accept a callback function to be invoked at the time that a spam message is about to be published.

[jm-clius]

Unlikely to be implemented with the new approach to RLN integration.