usermanagment.go
func (c *Client) AddUserToGroup(groupid string, userid string) (*User, error) {
	var usr User
	usr.ID = userid
	url := umGroupUsers(groupid) + `?depth=` + c.client.depth + `&pretty=` + strconv.FormatBool(c.client.pretty)
	ret := &User{}
	err := c.client.Post(url, usr, ret, http.StatusAccepted)
	return ret, err
}
func (c *Client) AddUserToGroup(groupid string, userid string) (*User, error) {
	var usr User
	usr.ID = userid
	url := umGroupUsers(groupid) + `?depth=` + c.client.depth + `&pretty=` + strconv.FormatBool(c.client.pretty)
	ret := &User{}
	err := c.client.Post(url, usr, ret, http.StatusAccepted)
	return ret, err
}
// AddUserToGroup adds a user to a group