Send peers the IRC listener user's QUIT reason (closes #216)

handleQuit now records the reason on the connection, and cleanup
passes it to BroadcastQuit, the same service call the HTTP API's
QUIT uses. A QUIT without a reason still gives Client quit. A
connection that ends without a QUIT still gives Connection closed.

The relay test that expected Connection closed for a bare QUIT now
expects Client quit.

Model: opus-5-5

internal/ircserver/conn.go

@@ -69,6 +69,11 @@ type Conn struct {
 	lastQueueID int64
 	closed      bool
 	killed      bool
+
+	// quitReason is the reason in the QUIT that peers are
+	// sent when the connection ends. The client's QUIT
+	// replaces it.
+	quitReason string
 }
 
 func newConn(
@@ -87,14 +92,15 @@ func newConn(
 	}
 
 	conn := &Conn{ //nolint:exhaustruct // zero-value defaults
-		conn:      tcpConn,
-		log:       log,
-		database:  database,
-		brk:       brk,
-		cfg:       cfg,
-		svc:       svc,
-		serverSfx: srvName,
-		remoteIP:  host,
+		conn:       tcpConn,
+		log:        log,
+		database:   database,
+		brk:        brk,
+		cfg:        cfg,
+		svc:        svc,
+		serverSfx:  srvName,
+		remoteIP:   host,
+		quitReason: "Connection closed",
 	}
 
 	conn.commands = conn.buildCommandMap()
@@ -278,6 +284,7 @@ func (c *Conn) cleanup(ctx context.Context) {
 	wasKilled := c.killed
 	sessID := c.sessionID
 	nick := c.nick
+	quitReason := c.quitReason
 	c.closed = true
 	c.mu.Unlock()
 
@@ -287,9 +294,7 @@ func (c *Conn) cleanup(ctx context.Context) {
 		// KILL has already sent the QUIT and deleted the
 		// session.
 		if !wasKilled {
-			c.svc.BroadcastQuit(
-				ctx, sessID, nick, "Connection closed",
-			)
+			c.svc.BroadcastQuit(ctx, sessID, nick, quitReason)
 		}
 	}