exp = [db_current_time.to_i + Rails.configuration.blob_signature_ttl,
trash_at].compact.map(&:to_i).min
self.class.sign_manifest manifest_text, token, exp
exp = [db_current_time.to_i + Rails.configuration.blob_signature_ttl,
trash_at].compact.map(&:to_i).min
self.class.sign_manifest manifest_text, token, exp