Include notification scheme customization options for bell notifications

Problem Definition

Currently the rules that govern if a in app bell notification is created is the same notification scheme used to govern email notifications.

If an admin wanted to turn off all email notifications yet only have in app ones this is currently not possible.

Suggested Solution

Create a separate notification scheme configuration for in-app notifications or the option to apply the current schemes to email, in-app or both.

Workaround

Disable outgoing mail, however this is not ideal as this is stie wide and not on a per-project basis.