code: func (c *Client) UpsertUser(user services.User) error {
  	data, err := services.GetUserMarshaler().MarshalUser(user)
  	if err != nil {
  		return trace.Wrap(err)
  	}
  	_, err = c.PostJSON(c.Endpoint("users"), &upsertUserRawReq{User: data})
  	return trace.Wrap(err)
  }
docs: // UpsertUser user updates or inserts user entry