Added Notification for Opening and Closing User Personal Sessions

Starting from V7Preview2, a notification UserSessionChanged has been added, which makes it easy to track changes to the property IUser.IsSessionOpen.

In some scenarios, personal sessions can be opened or closed simultaneously for a group of users, so the notification will contain a list of users whose personal session has been opened or closed, and the list may include both those whose personal session has just been opened and those whose personal session has just been closed.

In previous versions of the API, tracking personal sessions required using a more general notification UserChanged, which, as before, is triggered by any change to the user, including the opening and closing of personal sessions.

By the way, the plugin can not only monitor user personal sessions but also manage them.