The Thanks extension uses the Echo to send thanks - (https://gerrit.wikimedia.org/g/mediawiki/extensions/Thanks/+/9c8c711616954442ca7acb53452edf6f79628f50/includes/Api/ApiCoreThank.php#247).

It's straightforward to trigger Thanks notification and the notification itself is one of the simpler ones. We should migrate the Thanks Notification to use the newly built MediaWiki Notifications system.

Let's focus only on Core notification, no need to update flow notification as Flow is currently deprecated. (we've done them both)

Acceptance criteria:

• when Echo is not present, MediaWiki should send an email with Thanks notification (cancelled per T383995)
• when Echo is present, there is no visible behaviour to users

Note:
This task is strictly about triggering Thanks notification and it's to verify new MediaWiki notifications (and Echo provider) behaviour.