chanserv: SET founder and description

SET <#channel> FOUNDER <account> transfers ownership; SET DESC <text>
stores a description shown in INFO. Both are founder-gated and persisted
to the event log.

modules/chanserv/set.rs

@@ -0,0 +1,45 @@
+use crate::engine::db::Db;
+use crate::engine::service::{Sender, ServiceCtx};
+
+// SET <#channel> FOUNDER <account> | DESC <text>: founder-only channel settings.
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, db: &mut Db) {
+    let Some(&chan) = args.get(1) else {
+        ctx.notice(me, from.uid, "Syntax: SET <#channel> FOUNDER <account> | DESC <text>");
+        return;
+    };
+    let founder = match db.channel(chan) {
+        None => {
+            ctx.notice(me, from.uid, format!("\x02{chan}\x02 isn't registered."));
+            return;
+        }
+        Some(info) => info.founder.clone(),
+    };
+    if from.account != Some(founder.as_str()) {
+        ctx.notice(me, from.uid, format!("Only \x02{chan}\x02's founder can change its settings."));
+        return;
+    }
+    match args.get(2).map(|s| s.to_ascii_uppercase()).as_deref() {
+        Some("FOUNDER") => {
+            let Some(&account) = args.get(3) else {
+                ctx.notice(me, from.uid, "Syntax: SET <#channel> FOUNDER <account>");
+                return;
+            };
+            if !db.exists(account) {
+                ctx.notice(me, from.uid, format!("\x02{account}\x02 isn't a registered account."));
+                return;
+            }
+            match db.set_founder(chan, account) {
+                Ok(()) => ctx.notice(me, from.uid, format!("Founder of \x02{chan}\x02 transferred to \x02{account}\x02.")),
+                Err(_) => ctx.notice(me, from.uid, "Sorry, that didn't work. Please try again in a moment."),
+            }
+        }
+        Some("DESC") => {
+            let desc = if args.len() > 3 { args[3..].join(" ") } else { String::new() };
+            match db.set_desc(chan, &desc) {
+                Ok(()) => ctx.notice(me, from.uid, format!("Description for \x02{chan}\x02 updated.")),
+                Err(_) => ctx.notice(me, from.uid, "Sorry, that didn't work. Please try again in a moment."),
+            }
+        }
+        _ => ctx.notice(me, from.uid, "Syntax: SET <#channel> FOUNDER <account> | DESC <text>"),
+    }
+}