func isInternalHeader(headerKey string) bool {
	return strings.HasPrefix(headerKey, ":") || strings.EqualFold(headerKey, "host")
}

// isAuthorityHeader returns true if a header refers to the authority header
func isAuthorityHeader(headerKey string) bool {
	return strings.EqualFold(headerKey, ":authority") || strings.EqualFold(headerKey, "host")