HostServ: vhost OFFER menu, plus SETALL/DELALL/GROUP

A curated self-serve menu: operators OFFER <host> / OFFERDEL <n>, anyone
sees OFFERLIST, and a user picks one with TAKE <n> (assigned and applied
at once). Offers are a global event-sourced list (VhostOfferAdded/Removed,
threaded through apply like bots). SETALL/DELALL alias SET/DEL and GROUP
is a no-op reassurance, since the per-account vhost already covers every
grouped nick.

hostserv/src/offer.rs

@@ -0,0 +1,51 @@
+use fedserv_api::{Sender, ServiceCtx, Store};
+
+// OFFER <host>: add a vhost to the self-serve menu (operators).
+pub fn add(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    if !super::require_oper(me, from, ctx) {
+        return;
+    }
+    let Some(&host) = args.get(1) else {
+        ctx.notice(me, from.uid, "Syntax: OFFER <host>");
+        return;
+    };
+    if !super::valid_vhost(host) {
+        ctx.notice(me, from.uid, format!("\x02{host}\x02 isn't a valid host."));
+        return;
+    }
+    match db.vhost_offer_add(host) {
+        Ok(true) => ctx.notice(me, from.uid, format!("\x02{host}\x02 is now on the vhost menu.")),
+        Ok(false) => ctx.notice(me, from.uid, "That vhost is already on the menu."),
+        Err(_) => ctx.notice(me, from.uid, "Sorry, that didn't work. Please try again in a moment."),
+    }
+}
+
+// OFFERLIST: show the self-serve vhost menu (anyone).
+pub fn list(me: &str, from: &Sender, ctx: &mut ServiceCtx, db: &dyn Store) {
+    let offers = db.vhost_offers();
+    if offers.is_empty() {
+        ctx.notice(me, from.uid, "No vhosts are on offer.");
+        return;
+    }
+    ctx.notice(me, from.uid, format!("Vhosts on offer ({}):", offers.len()));
+    for (i, host) in offers.iter().enumerate() {
+        ctx.notice(me, from.uid, format!("  {}. {host}", i + 1));
+    }
+    ctx.notice(me, from.uid, "Take one with \x02TAKE\x02 <number>.");
+}
+
+// OFFERDEL <number>: remove an offer from the menu (operators).
+pub fn del(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    if !super::require_oper(me, from, ctx) {
+        return;
+    }
+    let Some(n) = args.get(1).and_then(|s| s.parse::<usize>().ok()) else {
+        ctx.notice(me, from.uid, "Syntax: OFFERDEL <number> (see OFFERLIST)");
+        return;
+    };
+    match db.vhost_offer_del(n) {
+        Ok(Some(host)) => ctx.notice(me, from.uid, format!("Removed \x02{host}\x02 from the menu.")),
+        Ok(None) => ctx.notice(me, from.uid, format!("There's no offer #\x02{n}\x02.")),
+        Err(_) => ctx.notice(me, from.uid, "Sorry, that didn't work. Please try again in a moment."),
+    }
+}