type IstioVersion string

// IstioVersions represents a collection of Istio versions running in a cluster.
type IstioVersions []IstioVersion

// NewIstioVersion creates an IstioVersion with validation.
func NewIstioVersion(s string) (IstioVersion, error) {
	// empty version string sentinel value for latest
	if s == "" {
		return "", nil
	}
	parts := strings.Split(s, ".")