Follow-up from the token expiration/removal spike (T259148). This can be done anytime after the MediaWiki code branch containing https://gerrit.wikimedia.org/r/c/mediawiki/extensions/Echo/+/619570/ is deployed to metawiki
On metawiki, create a bot account for the push-notifications service and add it to the newly created push-subscription-managers user group.
This can be done on mwmaint1002 using the maintenance script createAndPromote.php.
mwscript createAndPromote.php --wiki=metawiki --bot --custom-groups=push-subscription-manager WikimediaPushNotificationService