chore: use "mail" wording instead of "notification"

[Julien-R44]

Using "mail" wording instead of "notifications" since otherwise it will conflict with our future Notification package which also use the same term

[thetutlage]

The naming of emails as notification or provision is on purpose as they describe the intent for which they are created. So, I am not in favor of renaming them. But yeah, let's discuss how we can have both notifications and mails together. Also, haven't seen the notification package yet, so maybe I may have some thoughts after looking at it