Add optional export notifications (#3935)

* Add `emails.export_completed` notification to settings menu

Signed-off-by: AKP <tom@tdpain.net>

* Don't send email when export_completed notifications are disabled

Signed-off-by: AKP <tom@tdpain.net>

* Automatically subscribe new users to `export_completed` notifications

Signed-off-by: AKP <tom@tdpain.net>

* Alter secondary text on export page to mention optional notifications

Signed-off-by: AKP <tom@tdpain.net>

* Alter toast text on collection export for optional notifications

Signed-off-by: AKP <tom@tdpain.net>

* Only subscribe new admins to export notifs

Signed-off-by: AKP <tom@tdpain.net>

* Move `export_completed` notification decision into `beforeSend`

Signed-off-by: AKP <tom@tdpain.net>

* Update server/emails/templates/ExportFailureEmail.tsx

Co-authored-by: Tom Moor <tom.moor@gmail.com>

* Update server/emails/templates/ExportSuccessEmail.tsx

Co-authored-by: Tom Moor <tom.moor@gmail.com>

Signed-off-by: AKP <tom@tdpain.net>
Co-authored-by: Tom Moor <tom.moor@gmail.com>

server/models/NotificationSetting.ts

@@ -41,6 +41,7 @@ class NotificationSetting extends Model {
       "emails.invite_accepted",
       "emails.onboarding",
       "emails.features",
+      "emails.export_completed",
     ],
   ])
   @Column(DataType.STRING)