Stack notifications everywhere

We had client-side notification stacking in the tray since launch, but now we want to stack notifications in the notifications page, in API responses and in email bundles.

app/controllers/cards/readings_controller.rb

@@ -2,12 +2,12 @@ class Cards::ReadingsController < ApplicationController
   include CardScoped
 
   def create
-    @notifications = @card.read_by(Current.user)
+    @card.read_by(Current.user)
     record_board_access
   end
 
   def destroy
-    @notifications = @card.unread_by(Current.user)
+    @card.unread_by(Current.user)
     record_board_access
   end
 

app/controllers/notifications/trays_controller.rb

@@ -1,6 +1,6 @@
 class Notifications::TraysController < ApplicationController
   def show
-    @notifications = Current.user.notifications.preloaded.unread.ordered.limit(100)
+    @notifications = Current.user.notifications.unread.preloaded.ordered.limit(100)
 
     # Invalidate on the whole set instead of the unread set since the max updated at in the unread set
     # can stay the same when reading old notifications.