Per-user notification settings for new orders and subscriptions

[rishi-raj-jain]

from the ticket and the ticket

Make notification settings for new orders and subscriptions sync with per-user settings instead of org-level settings.

Currently, notification settings (for new orders, subscriptions) appear to be managed at the organization level. This should be changed to allow each user in the organization to manage their own notification preferences.

[pieterbeulque]

Related #8806 #6598