group.go
func (dom *Domain) Group(name string, members []*Account) *Group {
	return &Group{Domain: dom, Name: name, Members: members}
}
func (dom *Domain) Group(name string, members []*Account) *Group {
	return &Group{Domain: dom, Name: name, Members: members}
}
// Group creates a Group type from a domain, with the given name and members