server: brand the service pseudo-client host (was services.local)

The service pseudo-clients (NickServ etc.) wore a hardcoded services.local host,
so they showed as services@services.local. Add a configurable [server]
service_host (empty defaults to the server name), used when introducing them, so
they appear as services@services.tchatou.fr.

src/config.rs

@@ -261,6 +261,11 @@ pub struct Server {
     // ircd rejects a digit-leading SVSNICK and falls back to the raw uuid.
     #[serde(default = "default_guest_nick")]
     pub guest_nick: String,
+    // Hostname the service pseudo-clients wear (NickServ!services@<here>). Empty
+    // falls back to the server name, so NickServ shows as ...@services.tchatou.fr
+    // rather than the generic default.
+    #[serde(default)]
+    pub service_host: String,
 }
 
 fn default_protocol() -> u32 {

src/engine/mod.rs

@@ -102,6 +102,7 @@ pub struct Engine {
     // burst is done, so a relink doesn't enforce every already-online user.
     synced: bool,
     guest_nick: String, // base for the Guest#### rename on enforcement
+    service_host: String, // hostname the service pseudo-clients wear
     enforce_seq: u32,   // counter appended to guest_nick
     pending_enforce: Vec<PendingEnforce>, // registered nicks awaiting identify-or-rename
     bot_uids: HashMap<String, String>, // casefolded bot nick -> live uid (per connection)
@@ -229,6 +230,7 @@ impl Engine {
             sid: String::new(),
             synced: false,
             guest_nick: "Guest".to_string(),
+            service_host: "services.local".to_string(),
             enforce_seq: 0,
             pending_enforce: Vec::new(),
             bot_uids: HashMap::new(),
@@ -677,6 +679,13 @@ impl Engine {
         }
     }
 
+    // The hostname the service pseudo-clients wear (NickServ!services@<host>).
+    pub fn set_service_host(&mut self, host: &str) {
+        if !host.is_empty() {
+            self.service_host = host.to_string();
+        }
+    }
+
     // A user arrived on (or changed to) a registered nick: if they aren't logged
     // into that account, prompt them to IDENTIFY and schedule a rename. Gated on
     // `synced` so a netburst can't enforce every already-online user; a user who
@@ -808,7 +817,7 @@ impl Engine {
                 uid: svc.uid().to_string(),
                 nick: svc.nick().to_string(),
                 ident: "services".to_string(),
-                host: svc.host().to_string(),
+                host: self.service_host.clone(),
                 gecos: svc.gecos().to_string(),
             });
         }

src/main.rs

@@ -178,6 +178,9 @@ async fn main() -> Result<()> {
     engine.lock().await.set_opers(cfg.opers());
     engine.lock().await.set_sid(cfg.server.sid.clone());
     engine.lock().await.set_guest_nick(&cfg.server.guest_nick);
+    // Service pseudo-clients wear the configured host, or the server name.
+    let service_host = if cfg.server.service_host.is_empty() { &cfg.server.name } else { &cfg.server.service_host };
+    engine.lock().await.set_service_host(service_host);
     engine.lock().await.set_log_channel(cfg.log.as_ref().map(|l| l.channel.clone()));
     if let Some(expire) = &cfg.expire {
         engine.lock().await.set_expiry(expire.account_ttl(), expire.channel_ttl(), expire.warn_ttl());