Add notification policies and notification requests (#29366)

app/models/notification_request.rb

@@ -0,0 +1,53 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: notification_requests
+#
+#  id                  :bigint(8)        not null, primary key
+#  account_id          :bigint(8)        not null
+#  from_account_id     :bigint(8)        not null
+#  last_status_id      :bigint(8)        not null
+#  notifications_count :bigint(8)        default(0), not null
+#  dismissed           :boolean          default(FALSE), not null
+#  created_at          :datetime         not null
+#  updated_at          :datetime         not null
+#
+
+class NotificationRequest < ApplicationRecord
+  include Paginable
+
+  MAX_MEANINGFUL_COUNT = 100
+
+  belongs_to :account
+  belongs_to :from_account, class_name: 'Account'
+  belongs_to :last_status, class_name: 'Status'
+
+  before_save :prepare_notifications_count
+
+  def self.preload_cache_collection(requests)
+    cached_statuses_by_id = yield(requests.filter_map(&:last_status)).index_by(&:id) # Call cache_collection in block
+
+    requests.each do |request|
+      request.last_status = cached_statuses_by_id[request.last_status_id] unless request.last_status_id.nil?
+    end
+  end
+
+  def reconsider_existence!
+    return if dismissed?
+
+    prepare_notifications_count
+
+    if notifications_count.positive?
+      save
+    else
+      destroy
+    end
+  end
+
+  private
+
+  def prepare_notifications_count
+    self.notifications_count = Notification.where(account: account, from_account: from_account).limit(MAX_MEANINGFUL_COUNT).count
+  end
+end