Function directory_id 

pub(crate) fn directory_id(base_url: &str, account_sub: &str) -> String

Which directory a publication is for: the relay’s REST base plus the account (the token’s sub). The directory is keyed by account, and a relay move or a sign-in to another account is a directory that has never seen this install’s keys — so wan.db records publications per this id, and a key counts as published only to the directory it went to.