FEATURE: High priority bookmark reminder notifications (#9290)

Introduce the concept of "high priority notifications" which include PM and bookmark reminder notifications. Now bookmark reminder notifications act in the same way as PM notifications (float to top of recent list, show in the green bubble) and most instances of unread_private_messages in the UI have been replaced with unread_high_priority_notifications.

The user email digest is changed to just have a section about unread high priority notifications, the unread PM section has been removed.

A high_priority boolean column has been added to the Notification table and relevant indices added to account for it.

unread_private_messages has been kept on the User model purely for backwards compat, but now just returns unread_high_priority_notifications count so this may cause some inconsistencies in the UI.

app/models/notification.rb

@@ -44,6 +44,10 @@ class Notification < ActiveRecord::Base
     send_email unless NotificationConsolidator.new(self).consolidate!
   end
 
+  before_create do
+    self.high_priority = Notification.high_priority_types.include?(self.notification_type)
+  end
+
   def self.purge_old!
     return if SiteSetting.max_notifications_per_user == 0
 
@@ -64,10 +68,10 @@ class Notification < ActiveRecord::Base
   end
 
   def self.ensure_consistency!
-    DB.exec(<<~SQL, Notification.types[:private_message])
+    DB.exec(<<~SQL)
       DELETE
         FROM notifications n
-       WHERE notification_type = ?
+       WHERE high_priority
          AND NOT EXISTS (
             SELECT 1
               FROM posts p
@@ -108,6 +112,17 @@ class Notification < ActiveRecord::Base
                        )
   end
 
+  def self.high_priority_types
+    @high_priority_types ||= [
+      types[:private_message],
+      types[:bookmark_reminder]
+    ]
+  end
+
+  def self.normal_priority_types
+    @normal_priority_types ||= types.reject { |_k, v| high_priority_types.include?(v) }.values
+  end
+
   def self.mark_posts_read(user, topic_id, post_numbers)
     Notification
       .where(
@@ -210,14 +225,14 @@ class Notification < ActiveRecord::Base
 
     if notifications.present?
 
-      ids = DB.query_single(<<~SQL, count.to_i)
+      ids = DB.query_single(<<~SQL, limit: count.to_i)
          SELECT n.id FROM notifications n
          WHERE
-           n.notification_type = 6 AND
+           n.high_priority = TRUE AND
            n.user_id = #{user.id.to_i} AND
            NOT read
         ORDER BY n.id ASC
-        LIMIT ?
+        LIMIT :limit
       SQL
 
       if ids.length > 0
@@ -230,9 +245,9 @@ class Notification < ActiveRecord::Base
       end
 
       notifications.uniq(&:id).sort do |x, y|
-        if x.unread_pm? && !y.unread_pm?
+        if x.unread_high_priority? && !y.unread_high_priority?
           -1
-        elsif y.unread_pm? && !x.unread_pm?
+        elsif y.unread_high_priority? && !x.unread_high_priority?
           1
         else
           y.created_at <=> x.created_at
@@ -244,8 +259,8 @@ class Notification < ActiveRecord::Base
 
   end
 
-  def unread_pm?
-    Notification.types[:private_message] == self.notification_type && !read
+  def unread_high_priority?
+    self.high_priority? && !read
   end
 
   def post_id
@@ -280,14 +295,15 @@ end
 #  topic_id          :integer
 #  post_number       :integer
 #  post_action_id    :integer
+#  high_priority     :boolean          default(FALSE), not null
 #
 # Indexes
 #
 #  idx_notifications_speedup_unread_count                       (user_id,notification_type) WHERE (NOT read)
 #  index_notifications_on_post_action_id                        (post_action_id)
-#  index_notifications_on_read_or_n_type                        (user_id,id DESC,read,topic_id) UNIQUE WHERE (read OR (notification_type <> 6))
 #  index_notifications_on_topic_id_and_post_number              (topic_id,post_number)
 #  index_notifications_on_user_id_and_created_at                (user_id,created_at)
-#  index_notifications_on_user_id_and_id                        (user_id,id) UNIQUE WHERE ((notification_type = 6) AND (NOT read))
 #  index_notifications_on_user_id_and_topic_id_and_post_number  (user_id,topic_id,post_number)
+#  index_notifications_read_or_not_high_priority                (user_id,id DESC,read,topic_id) WHERE (read OR (high_priority = false))
+#  index_notifications_unique_unread_high_priority              (user_id,id) UNIQUE WHERE ((NOT read) AND (high_priority = true))
 #