Function server_setup_with 

pub fn server_setup_with<R: CryptoRng + ?Sized>(
    rng: &mut R,
    params: &Params,
    fac: &FacParams,
    setup_id: [u8; 32],
    server_id: &[u8],
) -> Result<(SetupData, ServerSetupSecret)>

Server setup with an explicit Π_fac group (tests).