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.

modules/memoserv/src/ignore.rs

@@ -0,0 +1,41 @@
+use echo_api::{Sender, ServiceCtx, Store};
+
+// IGNORE ADD <nick> | DEL <nick> | LIST: manage your memo-ignore list. Memos
+// from an ignored account are silently dropped.
+pub fn handle(me: &str, from: &Sender, account: &str, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    match args.get(1).map(|s| s.to_ascii_uppercase()).as_deref() {
+        Some("ADD") => {
+            let Some(&nick) = args.get(2) else {
+                ctx.notice(me, from.uid, "Syntax: IGNORE ADD <nick>");
+                return;
+            };
+            let target = db.resolve_account(nick).map(str::to_string).unwrap_or_else(|| nick.to_string());
+            if db.memo_ignore_add(account, &target) {
+                ctx.notice(me, from.uid, format!("Now ignoring memos from \x02{target}\x02."));
+            } else {
+                ctx.notice(me, from.uid, format!("You're already ignoring \x02{target}\x02."));
+            }
+        }
+        Some("DEL") | Some("REMOVE") => {
+            let Some(&nick) = args.get(2) else {
+                ctx.notice(me, from.uid, "Syntax: IGNORE DEL <nick>");
+                return;
+            };
+            let target = db.resolve_account(nick).map(str::to_string).unwrap_or_else(|| nick.to_string());
+            if db.memo_ignore_del(account, &target) {
+                ctx.notice(me, from.uid, format!("No longer ignoring \x02{target}\x02."));
+            } else {
+                ctx.notice(me, from.uid, format!("You weren't ignoring \x02{target}\x02."));
+            }
+        }
+        Some("LIST") | None => {
+            let list = db.memo_ignores(account);
+            if list.is_empty() {
+                ctx.notice(me, from.uid, "Your memo-ignore list is empty.");
+            } else {
+                ctx.notice(me, from.uid, format!("You're ignoring memos from: {}", list.join(", ")));
+            }
+        }
+        _ => ctx.notice(me, from.uid, "Syntax: IGNORE ADD <nick> | DEL <nick> | LIST"),
+    }
+}