ircv3: close server-support-table gaps — BOT=B ISUPPORT, account-extban (a: matcher + ACCOUNTEXTBAN=a), draft/read-marker cap (gates MARKREAD sync), and no-implicit-names (suppress the post-JOIN NAMES burst)

src/modules/accountban.rs

@@ -0,0 +1,16 @@
+//! The `a:` matching extban (IRCv3 account-extban): match a user by the services
+//! account they are logged into. `+b a:spammer` bans the account `spammer` (glob),
+//! `+e a:trusted` exempts one. A user with no account never matches. Dispatched
+//! from the channel ban matcher; advertised via `ACCOUNTEXTBAN=a`.
+
+use crate::channels::glob_match;
+use crate::server::Server;
+use crate::Uid;
+
+/// Does `uid`'s logged-in account match the glob `mask` (the part after `a:`)?
+pub fn matches(s: &Server, uid: Uid, mask: &str) -> bool {
+    match s.users.get(&uid).and_then(|u| u.account.as_deref()) {
+        Some(acct) => glob_match(mask, acct),
+        None => false, // not logged in — an account ban can't match
+    }
+}