Do not remove notification reference on NotificationClosed

In general we need to keep a reference to the notification id, so that
we can delete the notification later from history - unless the
NotificationClosed reason was that the user actively dismissed it, in
which case it is not kept in history anyway (so we can dismiss our
reference too).

-- Background --
Some desktop environments such as KDE keep a history of notifications.
An API is provided to delete notifications from that history by calling
the org.freedesktop.Notifications.CloseNotification endpoint with the ID
of that notification. If the notification was already closed (timed
out), then this will delete the notification from history.

The intent is to clear these notifications from the notification history
as soon as a chat with notifications originating from that person is
opened, as the user is then not interested anymore in those
notifications and to prevent unnecessary clutter in the history widget.
It is also cleared when the chat is read on another device.

-- Problem --
Telegram already has all the code in place to support this
functionality, but unfortunately this did not work on Linux before,
because we listen to the NotificationClosed signal and remove our
reference to the notification id from our internal manager as soon as we
get that signal. This means that we do not clear that notification from
history once we open the chat with that person (unless we open the chat
before the notification has timed out, i.e. if we didn't get the
NotificationClosed signal).

-- Fix --
To fix this, we keep our notification reference (if the notification was
not dismissed by the user), which means that our reference will be kept
around until we open the chat with that person (or close Telegram
entirely).

Since all the needed functionality for deleting notifications was
already in place, this patch is quite short as we only need to keep the
reference around longer than we did before this patch.

Note also that code is already in place to clear notifications for
messages that were read on another device: History::inboxRead() calls
Core::App().notifications().clearIncomingFromHistory()

Fixes #17111

Telegram/SourceFiles/history/history_inner_widget.cpp

@@ -2570,7 +2570,7 @@ void HistoryInner::checkHistoryActivation() {
 	}
 	adjustCurrent(_visibleAreaBottom);
 	if (_history->loadedAtBottom() && _visibleAreaBottom >= height()) {
-		// Clear possible scheduled messages notifications.
+		// Clear possible message notifications.
 		Core::App().notifications().clearFromHistory(_history);
 	}
 	if (_curHistory != _history || _history->isEmpty()) {

Telegram/SourceFiles/platform/linux/notifications_manager_linux.cpp

@@ -695,7 +695,21 @@ void NotificationData::setImage(const QString &imagePath) {
 }
 
 void NotificationData::notificationClosed(uint id, uint reason) {
-	if (id == _notificationId) {
+	/*
+	 * From: https://specifications.freedesktop.org/notification-spec/latest/ar01s09.html
+	 * The reason the notification was closed
+	 * 1 - The notification expired.
+	 * 2 - The notification was dismissed by the user.
+	 * 3 - The notification was closed by a call to CloseNotification.
+	 * 4 - Undefined/reserved reasons.
+	 *
+	 * If the notification was dismissed by the user (reason == 2), the notification is not kept in notification history.
+	 * We do not need to send a "CloseNotification" call later to clear it from history.
+	 * Therefore we can drop the notification reference now.
+	 * In all other cases we keep the notification reference so that we may clear the notification later from history,
+	 * if the message for that notification is read (e.g. chat is opened or read from another device).
+	*/
+	if (id == _notificationId && reason == 2) {
 		_manager->clearNotification(_id);
 	}
 }