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

app/models/content_retention_policy.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+class ContentRetentionPolicy
+  def self.current
+    new
+  end
+
+  def media_cache_retention_period
+    retention_period Setting.media_cache_retention_period
+  end
+
+  def content_cache_retention_period
+    retention_period Setting.content_cache_retention_period
+  end
+
+  def backups_retention_period
+    retention_period Setting.backups_retention_period
+  end
+
+  private
+
+  def retention_period(value)
+    value.days if value.is_a?(Integer) && value.positive?
+  end
+end