List the user modes in the 004 reply (closes #220)

Both transports sent an empty string as the user modes in RPL_MYINFO.
On the IRC listener that left an empty parameter in the middle of the
line, so a client that splits on spaces read the channel modes as the
user modes. The reply now lists o and w, the user modes the server
supports. Both transports read them from one constant in
internal/service, next to the code that decides which user modes MODE
accepts. The README and the schema notes now show what the HTTP API
sends.

Model: opus-5-5

internal/handlers/api.go

@@ -412,7 +412,7 @@ func (hdlr *Handlers) deliverWelcome(
 	// 004 RPL_MYINFO
 	hdlr.enqueueNumeric(
 		ctx, clientID, irc.RplMyInfo, nick,
-		[]string{srvName, version, "", "ikmnostl"},
+		[]string{srvName, version, service.UserModes, "ikmnostl"},
 		"",
 	)
 

internal/handlers/api_test.go

@@ -6797,6 +6797,30 @@ func TestISUPPORT(t *testing.T) {
 	}
 }
 
+// TestMyInfoListsUserModes verifies the 004 numeric lists
+// the user modes o and w as its third parameter.
+func TestMyInfoListsUserModes(t *testing.T) {
+	t.Parallel()
+
+	tserver := newTestServer(t)
+	token := tserver.createSession("myinfo")
+
+	msgs, _ := tserver.pollMessages(token, 0)
+
+	myInfo := findNumericWithParams(msgs, "004")
+	if myInfo == nil {
+		t.Fatal("expected 004 RPL_MYINFO")
+	}
+
+	params := getNumericParams(myInfo)
+	if len(params) != 4 || params[2] != "ow" {
+		t.Fatalf(
+			"004 params %v, want four with user modes ow third",
+			params,
+		)
+	}
+}
+
 // TestNonOpCannotSetModes verifies non-operators
 // cannot set +i, +s, +k, +l, +b.
 func TestNonOpCannotSetModes(t *testing.T) {