code: func (u *UsersClient) Create(ctx context.Context, userObj *envelope.User,
  	signup apitypes.Signup) (envelope.UserInf, error) {
  
  	v := &url.Values{}
  	if signup.InviteCode != "" {
  		v.Set("code", signup.InviteCode)
  	}
  	if signup.OrgInvite && signup.OrgName != "" {
  		v.Set("org", signup.OrgName)
  	}
  	if signup.Email != "" {
  		v.Set("email", signup.Email)
  	}
  
  	e := envelope.Unsigned{}
  	err := u.client.RoundTrip(ctx, "POST", "/users", v, &userObj, &e)
  	if err != nil {
  		return nil, err
  	}
  
  	return envelope.ConvertUser(&e)
  }
docs: // Create attempts to register a new user