Add migration (#103)

lib/tasks/data_migration/backfill_subscribers_to_announcements_mailing_list.rake

@@ -0,0 +1,22 @@
+# typed: strict
+# frozen_string_literal: true
+
+extend Rake::DSL # rubocop:disable Style/MixinUsage
+
+namespace :data_migration do
+  desc "Backfill the first_approved_at date for already approved reviews"
+  task backfill_subscribers_to_announcements_mailing_list: :environment do
+    Rails.logger = Logger.new($stdout)
+    ActiveRecord::Base.logger = Rails.logger
+
+    # Change to :debug for ActiveRecord SQL logs.
+    Rails.logger.level = :info
+
+    ActiveRecord::Base.transaction do
+      User.all.find_each do |user|
+        user.subscribe("announcements") unless user.subscribed?("announcements")
+        user.save
+      end
+    end
+  end
+end