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.

test/models/notification/bundle_test.rb

@@ -5,6 +5,7 @@ class Notification::BundleTest < ActiveSupport::TestCase
 
   setup do
     @user = users(:david)
+    @user.notifications.destroy_all
     @user.settings.bundle_email_every_few_hours!
   end
 
@@ -25,7 +26,7 @@ class Notification::BundleTest < ActiveSupport::TestCase
     end
   end
 
-  test "notifications are bundled withing the aggregation period" do
+  test "notifications are bundled within the aggregation period" do
     @user.notification_bundles.destroy_all
 
     notification_1 = assert_difference -> { @user.notification_bundles.pending.count }, 1 do
@@ -34,12 +35,12 @@ class Notification::BundleTest < ActiveSupport::TestCase
     travel_to 3.hours.from_now
 
     notification_2 = assert_no_difference -> { @user.notification_bundles.count } do
-      @user.notifications.create!(source: events(:logo_published), creator: @user)
+      @user.notifications.create!(source: events(:layout_published), creator: @user)
     end
     travel_to 3.days.from_now
 
     notification_3 = assert_difference -> { @user.notification_bundles.pending.count }, 1 do
-      @user.notifications.create!(source: events(:logo_published), creator: @user)
+      @user.notifications.create!(source: events(:text_published), creator: @user)
     end
 
     assert_equal 2, @user.notification_bundles.count
@@ -150,10 +151,10 @@ class Notification::BundleTest < ActiveSupport::TestCase
 
   test "out-of-order notification bundling should still work" do
     first_notification = @user.notifications.create!(source: events(:logo_published), creator: @user)
-    second_notification = @user.notifications.create!(source: events(:logo_published), creator: @user)
+    second_notification = @user.notifications.create!(source: events(:layout_commented), creator: @user)
     @user.notification_bundles.destroy_all
 
-    assert first_notification.created_at < second_notification.created_at
+    assert first_notification.updated_at <= second_notification.updated_at
     @user.bundle(second_notification)
     @user.bundle(first_notification)