Extend notifications to be marked as read and unread

db/migrate/20180222120017_add_read_at_to_notifications.rb

@@ -0,0 +1,5 @@
+class AddReadAtToNotifications < ActiveRecord::Migration
+  def change
+    add_column :notifications, :read_at, :timestamp
+  end
+end

db/schema.rb

@@ -12,7 +12,6 @@
 # It's strongly recommended that you check this file into your version control system.
 
 ActiveRecord::Schema.define(version: 20180320104823) do
-
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"
   enable_extension "unaccent"
@@ -640,6 +639,7 @@ ActiveRecord::Schema.define(version: 20180320104823) do
     t.string   "notifiable_type"
     t.integer  "counter",         default: 1
     t.datetime "emailed_at"
+    t.datetime "read_at"
   end
 
   add_index "notifications", ["user_id"], name: "index_notifications_on_user_id", using: :btree