Receiver::pj_url is missing fragment parameters

[spacebear21]

According to the docstring:

    // The contents of the `&pj=` query parameter.
    // This identifies a session at the payjoin directory server.
    pub fn pj_url(&self) -> Url {

But the return value only contains the subdirectory (e.g. https://payjo.in/4A8JZNN5SD9EV) and is missing the hpke pubkey, ohttp keys, and expiration in fragment parameters.