MediaWiki allows to trigger Email Notifications to specified set of Administrators. By setting the UsersNotifiedOnAllChanges config flag we can define a list of people who will receive emails after every on wiki change.

Migrate this system into the newly created Notifications component. This will allow to validate the idea without disrupting existing Watchlist notifications.
This feature is not used on WMF wikis, therefore this change shouldn't have any impact for our services.

Acceptance Criteria:

• MediaWiki provides a Notification to represent a RecentChange
• MediaWiki provides a RecentNotitifcationChangeHandler to handle notifications regarding page updates
• RecentNotitifcationChangeHandler sends emails only to people with confirmed emails
• RecentNotitifcationChangeHandler uses service from T387987 to trigger Emails
• When UsersNotifiedOnAllChanges config is set, the new system and notification is used to trigger emails