code: func (ra *RegistrationAuthorityImpl) DeactivateRegistration(ctx context.Context, reg core.Registration) error {
  	if reg.Status != core.StatusValid {
  		return berrors.MalformedError("only valid registrations can be deactivated")
  	}
  	err := ra.SA.DeactivateRegistration(ctx, reg.ID)
  	if err != nil {
  		return berrors.InternalServerError(err.Error())
  	}
  	return nil
  }
docs: // DeactivateRegistration deactivates a valid registration