HostServ: vhost request/approval flow

REQUEST <host> records a pending vhost (typed Option<PendingVhost> on the
account, VhostRequested/VhostRequestCleared events); operators review with
WAITING and either ACTIVATE (assign + apply to online sessions) or REJECT
(clear it). Host validation and the operator gate are shared with SET.

hostserv/src/request.rs

@@ -0,0 +1,21 @@
+use fedserv_api::{Sender, ServiceCtx, Store};
+
+// REQUEST <host>: ask for a vhost, to be approved by an operator.
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, db: &mut dyn Store) {
+    let Some(account) = from.account else {
+        ctx.notice(me, from.uid, "You need to identify to NickServ first.");
+        return;
+    };
+    let Some(&host) = args.get(1) else {
+        ctx.notice(me, from.uid, "Syntax: REQUEST <host>");
+        return;
+    };
+    if !super::valid_vhost(host) {
+        ctx.notice(me, from.uid, format!("\x02{host}\x02 isn't a valid host (letters, digits, hyphens and dots)."));
+        return;
+    }
+    match db.request_vhost(account, host) {
+        Ok(()) => ctx.notice(me, from.uid, format!("Requested vhost \x02{host}\x02 — an operator will review it.")),
+        Err(_) => ctx.notice(me, from.uid, "Sorry, that didn't work. Please try again in a moment."),
+    }
+}