improve the notification performance

This improvements has two parts:
* Avoid reapplying the visibility check for notifications.
* Merging the constraints rather then having them in a subselect.

lib/api/v3/notifications/notifications_api.rb

@@ -60,8 +60,10 @@ def bulk_update_status(attributes)
             end
           end
 
+          # No need to reapply the visibility scope here as this will be done by the used
+          # NotificationQuery.
           get &::API::V3::Utilities::Endpoints::SqlFallbackedIndex
-            .new(model: Notification, scope: -> { notification_scope })
+            .new(model: Notification, scope: -> { Notification.where.not(read_ian: nil) })
             .mount
 
           post :read_ian do

lib/api/v3/utilities/endpoints/index.rb

@@ -164,7 +164,7 @@ def apply_scope_constraint(constraint, result_scope)
             else
               result_scope
                 .includes(constraint.includes_values)
-                .where id: constraint.select(:id)
+                .merge constraint
             end
           end
         end