nickserv: AJOIN auto-join list

Adds the account auto-join list (AJOIN ADD/DEL/LIST): NickServ SVSJOINs you
into your listed channels each time you identify. The list is a typed
Vec<AjoinEntry> on the account, folded through the event log like the cert and
akick lists (persists and replays; no separate store), reached by modules
through the Store trait. New ForceJoin action serialises to InspIRCd SVSJOIN.
Shown in INFO. Operates on the caller's own account; the oper form for other
users waits on a privilege system.

src/grpc.rs

@@ -122,6 +122,8 @@ fn to_wire(entry: &LogEntry) -> Option<ReplicationEvent> {
         Event::CertAdded { .. }
         | Event::CertRemoved { .. }
         | Event::AccountPasswordSet { .. }
+        | Event::AjoinAdded { .. }
+        | Event::AjoinRemoved { .. }
         | Event::ChannelMlock { .. }
         | Event::ChannelAccessAdd { .. }
         | Event::ChannelAccessDel { .. }
@@ -351,6 +353,7 @@ mod tests {
             scram512: None,
             certfps: vec!["deadbeef".into()],
             verified: true,
+            ajoin: vec![],
         };
         let registered = LogEntry::for_test("A", 0, 1, Event::AccountRegistered(acct));
         let wire = to_wire(&registered).expect("account registration replicates");