Notifications Emails

[uhrjun]

Is your feature request related to a problem? Please describe.
Need to open drive to keep checking for notifications.

Describe the solution you'd like
Shared and mention notifications should send out emails. The user receiving the notification should be able to switch off email notifications, they should also be able to configure whether they want to get an email only when a file is directly shared with them. Effectively, omitting group shares/mentions and organization.