func (filter FilterRule) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
	if filter.isEmpty() {
		return nil
	}
	type filterRuleWrapper FilterRule
	return e.EncodeElement(filterRuleWrapper(filter), start)
}

// UnmarshalXML - decodes XML data.
func (filter *FilterRule) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
	// Make subtype to avoid recursive UnmarshalXML().

type Site struct {
	Name   string
	Region string
}

var validRegionRegex = regexp.MustCompile("^[a-zA-Z][a-zA-Z0-9-_-]+$")

// validSiteNameRegex - allows lowercase letters, digits and '-', starts with
// letter. At least 2 characters long.
var validSiteNameRegex = regexp.MustCompile("^[a-z][a-z0-9-]+$")

// LookupSite - get site related configuration. Loads configuration from legacy
// region sub-system as well.