Blake2: add modern interface using Nat

[NicolasDP]

Just continuing the improvements started with Cryptonite.Hash.SHAKE.

[ocheron]

BLAKE2 is defined with a maximum digest size.
Is it possible to add this contraint using the operators from GHC.TypeLits ?

[NicolasDP]

That's a good idea. I will see if I can come with something in Crypto.Internal.Nat.

[NicolasDP]

Now, with base >= 4.9.0, we can have the nice following output:

/Users/nicolas/work/primetype/haskell-crypto/cryptonite/tests/Hash.hs:202:23: error:
    • bitlen 1024 is greater than 512
      You have tried to use an invalid Digest size. Please, refer to the documentation.
    • In the expression: HashAlg (Blake2b :: Blake2b 1024)
      In the expression:
        ("Blake2b 512", HashAlg (Blake2b :: Blake2b 1024), 
      ...

Also added the minimal constraint of 1 byte.

[vincenthz]

Nice, thanks !