chanserv: entrymsg, enforce, getkey, seen, clone, aop/sop/vop

Tracks channel membership (join/part/kick), the current key, and per-nick
last-seen in the network view. Entry messages greet joiners; enforce
re-applies the lock, access modes and auto-kicks to everyone present;
getkey reports the key; seen reports last activity; clone copies a
channel's settings; aop/sop/vop are tiered shortcuts over the access list.

modules/chanserv/getkey.rs

@@ -0,0 +1,19 @@
+use crate::engine::db::Db;
+use crate::engine::service::{Sender, ServiceCtx};
+use crate::engine::state::Network;
+
+// GETKEY <#channel>: report the channel key (+k), for ops who need to let
+// someone in.
+pub fn handle(me: &str, from: &Sender, args: &[&str], ctx: &mut ServiceCtx, net: &Network, db: &Db) {
+    let Some(&chan) = args.get(1) else {
+        ctx.notice(me, from.uid, "Syntax: GETKEY <#channel>");
+        return;
+    };
+    if !super::require_op(me, from, chan, ctx, db) {
+        return;
+    }
+    match net.channel_key(chan) {
+        Some(key) => ctx.notice(me, from.uid, format!("Key for \x02{chan}\x02 is \x02{key}\x02.")),
+        None => ctx.notice(me, from.uid, format!("\x02{chan}\x02 has no key set.")),
+    }
+}