Function schnorrkel::context::attach_rng

pub fn attach_rng<T, R>(t: T, rng: R) -> SigningTranscriptWithRng<T, R> where
    T: SigningTranscript,
    R: RngCore + CryptoRng, 

Attach a CryptoRng to a SigningTranscript to repalce the default ThreadRng

There are tricks like attach_rng(t,ChaChaRng::from_seed([0u8; 32])) for deterministic tests. We warn against doing this in production however because, although such derandomization produces secure Schnorr signatures, we do implement protocols here like multi-signatures which likely become vulnerabile when derandomized.