Add task to delete bad SubscriberLists

These lists were created by accident in April 2023, the active
subscribers were migrated away from the lists by this PR:
#1948

The lists will delete automatically, but not for a year because
of the one-year retention period for ended subscriptions. In this
case, the data is confusing so worthwhile clearing up earlier.

We won't touch the Subscribers, they'll be retained for a year if
they have no active subscriptions, then cleared up automatically.

lib/bad_list_deleter.rb

@@ -0,0 +1,56 @@
+class BadListDeleter
+  VALID_PREFIXES = %w[
+    topic
+    organisations
+    government/people
+    government/ministers
+    government/topical-events
+    service-manual
+    service-manual/service-standard
+  ].freeze
+
+  attr_reader :prefix
+
+  def initialize(prefix)
+    @prefix = prefix
+  end
+
+  def process_all_lists
+    message = "Bad list deletion not possible for the provided prefix"
+    raise message unless valid_prefix?
+
+    bad_lists.each do |bad_list|
+      if bad_list.subscriptions.active.any?
+        next
+      end
+
+      bad_list.destroy!
+    end
+  end
+
+  def bad_lists
+    subscriber_lists - valid_links_based_lists?(subscriber_lists)
+  end
+
+private
+
+  def valid_prefix?
+    VALID_PREFIXES.include?(prefix)
+  end
+
+  def subscriber_lists
+    @subscriber_lists ||= SubscriberList.where("url LIKE ?", "%/#{prefix}/%")
+  end
+
+  def valid_links_based_lists?(lists)
+    lists.select { |list| valid_links_based_list?(list) }
+  end
+
+  def valid_links_based_list?(list)
+    list.content_id.nil? && has_links_or_tags(list)
+  end
+
+  def has_links_or_tags(list)
+    list.links.present? || list.tags.present?
+  end
+end

lib/tasks/data_cleanup.rake

@@ -0,0 +1,12 @@
+desc "Update one of the tags in a subscriber list"
+task delete_bad_lists: :environment do |_t, _args|
+  BadListDeleter::VALID_PREFIXES.each do |prefix|
+    deleter = BadListDeleter.new(prefix)
+
+    bad_lists = deleter.bad_lists
+    subscriptions_sum = bad_lists.sum { |l| l.subscriptions.ended.count }
+    puts "Prefix: #{prefix} attempting to delete #{bad_lists.count} lists and #{subscriptions_sum} subscriptions"
+    deleter.process_all_lists
+    puts " - #{deleter.bad_lists.count} could not be deleted" if deleter.bad_lists.any?
+  end
+end