Add notification policies and notification requests (#29366)

app/models/notification_policy.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+# == Schema Information
+#
+# Table name: notification_policies
+#
+#  id                      :bigint(8)        not null, primary key
+#  account_id              :bigint(8)        not null
+#  filter_not_following    :boolean          default(FALSE), not null
+#  filter_not_followers    :boolean          default(FALSE), not null
+#  filter_new_accounts     :boolean          default(FALSE), not null
+#  filter_private_mentions :boolean          default(TRUE), not null
+#  created_at              :datetime         not null
+#  updated_at              :datetime         not null
+#
+
+class NotificationPolicy < ApplicationRecord
+  belongs_to :account
+
+  has_many :notification_requests, primary_key: :account_id, foreign_key: :account_id, dependent: nil, inverse_of: false
+
+  attr_reader :pending_requests_count, :pending_notifications_count
+
+  MAX_MEANINGFUL_COUNT = 100
+
+  def summarize!
+    @pending_requests_count = pending_notification_requests.first
+    @pending_notifications_count = pending_notification_requests.last
+  end
+
+  private
+
+  def pending_notification_requests
+    @pending_notification_requests ||= notification_requests.where(dismissed: false).limit(MAX_MEANINGFUL_COUNT).pick(Arel.sql('count(*), coalesce(sum(notifications_count), 0)::bigint'))
+  end
+end