Deliver emails for bundled notifications (initial WIP)

app/models/user.rb

@@ -1,5 +1,5 @@
 class User < ApplicationRecord
-  include Accessor, Attachable, Assignee, Mentionable, Named, Role, Searcher,
+  include Accessor, Attachable, Assignee, Mentionable, Named, Notifiable, Role, Searcher,
     SignalUser, Staff, Transferable, Conversational
   include Timelined # Depends on Accessor
 
@@ -10,8 +10,6 @@ class User < ApplicationRecord
 
   has_many :comments, inverse_of: :creator, dependent: :destroy
 
-  has_many :notifications, dependent: :destroy
-
   has_many :filters, foreign_key: :creator_id, inverse_of: :creator, dependent: :destroy
   has_many :closures, dependent: :nullify
   has_many :pins, dependent: :destroy