pub fn to_qrcode_url(&self) -> String {
        let param = format!("{}:{}@{}", self.method(), self.password(), self.addr());
        format!("ss://{}", URL_PASSWORD_BASE64_ENGINE.encode(param))
    }
Get URL for QRCode
```plain
ss:// + base64(method:password@host:port)
```
crates/shadowsocks/src/config.rs