code: func removeCA(c context.Context, name string, rev string) error {
  	return ds.RunInTransaction(c, func(c context.Context) error {
  		existing := CA{CN: name}
  		if err := ds.Get(c, &existing); err != nil {
  			return err
  		}
  		if existing.Removed {
  			return nil
  		}
  		logging.Infof(c, "Removing CA %q", name)
  		existing.Removed = true
  		existing.RemovedRev = rev
  		return ds.Put(c, &existing)
  	}, nil)
  }
docs: // removeCA marks the CA in the datastore as removed.