code: func (c *ExampleService) UpdateUser(ctx context.Context, id platform.ID, upd platform.UserUpdate) (*platform.User, error) {
  	var u *platform.User
  	err := c.kv.Update(func(tx Tx) error {
  		usr, err := c.updateUser(ctx, tx, id, upd)
  		if err != nil {
  			return err
  		}
  		u = usr
  		return nil
  	})
  
  	if err != nil {
  		return nil, &platform.Error{
  			Err: err,
  			Op:  "kv/" + platform.OpUpdateUser,
  		}
  	}
  
  	return u, nil
  }
docs: // UpdateUser updates a example according the parameters set on upd.