Add last_time_changed_at columnd to SystemNotifications

app/models/system_notification.rb

@@ -5,6 +5,6 @@ class SystemNotification < ApplicationRecord
   has_many :users, through: :user_system_notifications
 
   validates :title, :modal_title, :modal_body, :description,
-            :source_created_at, :source_id,
+            :source_created_at, :source_id, :last_time_changed_at,
             presence: true
 end

db/migrate/20190125122852_create_system_notifications.rb

@@ -10,6 +10,7 @@ class CreateSystemNotifications < ActiveRecord::Migration[5.1]
       t.boolean :show_on_login, default: false
       t.datetime :source_created_at, index: true
       t.bigint :source_id, index: true, unique: true
+      t.datetime :last_time_changed_at, index: true, null: false
 
       t.timestamps
     end

db/schema.rb

@@ -668,8 +668,10 @@ ActiveRecord::Schema.define(version: 20190125123107) do
     t.boolean "show_on_login", default: false
     t.datetime "source_created_at"
     t.bigint "source_id"
+    t.datetime "last_time_changed_at", null: false
     t.datetime "created_at", null: false
     t.datetime "updated_at", null: false
+    t.index ["last_time_changed_at"], name: "index_system_notifications_on_last_time_changed_at"
     t.index ["source_created_at"], name: "index_system_notifications_on_source_created_at"
     t.index ["source_id"], name: "index_system_notifications_on_source_id"
   end

spec/factories/system_notifications.rb

@@ -8,6 +8,7 @@ FactoryBot.define do
     modal_body { Faker::Lorem.paragraphs(4).map { |pr| "<p>#{pr}</p>" }.join }
     source_created_at { Faker::Time.between(3.days.ago, Date.today) }
     source_id { Faker::Number.between(1, 1000) }
+    last_time_changed_at { Time.now }
     trait :show_on_login do
       show_on_login { true }
     end

spec/models/system_notification_spec.rb

@@ -33,6 +33,10 @@ describe SystemNotification do
     describe '#source_created_at' do
       it { is_expected.to validate_presence_of(:source_created_at) }
     end
+
+    describe '#last_time_changed_at' do
+      it { is_expected.to validate_presence_of(:last_time_changed_at) }
+    end
   end
 
   describe 'Associations' do