internal/coding/idheader.go
func FromIDHeader(v string) string {
	if v == "" {
		return v
	}
	v = strings.TrimLeft(v, "<")
	v = strings.TrimRight(v, ">")
	r, err := url.QueryUnescape(v)
	if err != nil {
		return v
	}
	return r
}
func FromIDHeader(v string) string {
	if v == "" {
		return v
	}
	v = strings.TrimLeft(v, "<")
	v = strings.TrimRight(v, ">")
	r, err := url.QueryUnescape(v)
	if err != nil {
		return v
	}
	return r
}
// FromIDHeader decodes a Content-ID or Message-ID header value (RFC 2392) into a utf-8 string.
// Example: "<foo%3fbar+baz>" becomes "foo?bar baz".