MemoServ: add IGNORE

IGNORE ADD/DEL/LIST manages a per-account memo-ignore list; a memo from
an ignored account is silently dropped, and the sender is still told it
was sent so the ignore isn't revealed. New memo_ignore account field +
events, and a check in SEND.

src/grpc.rs

@@ -139,6 +139,8 @@ fn to_wire(entry: &LogEntry) -> Option<ReplicationEvent> {
         | Event::MemoSent { .. }
         | Event::MemoRead { .. }
         | Event::MemoDeleted { .. }
+        | Event::MemoIgnoreAdd { .. }
+        | Event::MemoIgnoreDel { .. }
         | Event::ChannelMlock { .. }
         | Event::ChannelAccessAdd { .. }
         | Event::ChannelAccessDel { .. }
@@ -454,6 +456,7 @@ mod tests {
             ajoin: vec![],
             suspension: None,
             memos: vec![],
+            memo_ignore: vec![],
             greet: String::new(),
             vhost: None,
             vhost_request: None,