// unicode.IsSpace() internally here) to one space and return
	return strings.Join(strings.Fields(input), " ")
}

// checkMetaHeaders will check if the metadata from header/url is the same with the one from signed headers
func checkMetaHeaders(signedHeadersMap http.Header, r *http.Request) APIErrorCode {
	// check values from http header
	for k, val := range r.Header {