Add notification policies and notification requests (#29366)

app/models/notification_permission.rb

@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: notification_permissions
+#
+#  id              :bigint(8)        not null, primary key
+#  account_id      :bigint(8)        not null
+#  from_account_id :bigint(8)        not null
+#  created_at      :datetime         not null
+#  updated_at      :datetime         not null
+#
+class NotificationPermission < ApplicationRecord
+  belongs_to :account
+  belongs_to :from_account, class_name: 'Account'
+end