type: string
                        uri:
                          description: rewrite the path (or the prefix) portion of
                            the URI with this value.
                          type: string
                        uriRegexRewrite:
                          description: rewrite the path portion of the URI with the
                            specified regex.

// If input is nil an empty map is returned, not nil.
func cloneMSS(v map[string]string) map[string]string {
	r := make(map[string]string, len(v))
	for k, v := range v {
		r[k] = v
	}
	return r
}

// URI scheme constants.
const (
	httpScheme  = "http"
	httpsScheme = "https"
)

// nopCharsetConverter is a dummy charset convert which just copies input to output,