* Add documentation for GET /api/v1/notifications/policy
* Add documentation for `PATCH /api/v1/notifications/policy`
* Add documentation for `GET /api/v1/notifications/requests`
* Add documentation for `GET /api/v1/notifications/requests/:id`
* Add documentation for accepting and rejecting requests
* Remove redundant HTTP request examples
* Add documentation for the `NotificationPolicy` entity
* Add documentation for the `NotificationRequest` entity
