Add retention policy for cached content and media (#19232)

app/lib/vacuum/preview_cards_vacuum.rb

@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+class Vacuum::PreviewCardsVacuum
+  TTL = 1.day.freeze
+
+  def initialize(retention_period)
+    @retention_period = retention_period
+  end
+
+  def perform
+    vacuum_cached_images! if retention_period?
+    vacuum_orphaned_records!
+  end
+
+  private
+
+  def vacuum_cached_images!
+    preview_cards_past_retention_period.find_each do |preview_card|
+      preview_card.image.destroy
+      preview_card.save
+    end
+  end
+
+  def vacuum_orphaned_records!
+    orphaned_preview_cards.in_batches.destroy_all
+  end
+
+  def preview_cards_past_retention_period
+    PreviewCard.cached.where(PreviewCard.arel_table[:updated_at].lt(@retention_period.ago))
+  end
+
+  def orphaned_preview_cards
+    PreviewCard.where('NOT EXISTS (SELECT 1 FROM preview_cards_statuses WHERE preview_cards_statuses.preview_card_id = preview_cards.id)').where(PreviewCard.arel_table[:created_at].lt(TTL.ago))
+  end
+
+  def retention_period?
+    @retention_period.present?
+  end
+end