code: func newRetentionEnforcer(engine Deleter, bucketService BucketFinder) *retentionEnforcer {
  	s := &retentionEnforcer{
  		Engine:        engine,
  		BucketService: bucketService,
  		logger:        zap.NewNop(),
  	}
  	s.metrics = newRetentionMetrics(nil)
  	return s
  }
docs: // newRetentionEnforcer returns a new enforcer that ensures expired data is
  // deleted every interval period. Setting interval to 0 is equivalent to
  // disabling the service.