s3s: dto: copy_source

    /// Returns an error if the header is invalid

    pub fn parse(header: &str) -> Result<Self, ParseCopySourceError> {

        let header = urlencoding::decode(header).map_err(|_| ParseCopySourceError::InvalidEncoding)?;

        let header = header.strip_prefix('/').unwrap_or(&header);

        // FIXME: support access point

        match header.split_once('/') {