multi-hot, or tf-idf encoded representations
    *   `CategoryCrossing`: create new categorical features representing
        co-occurrences of previous categorical feature values
    *   `Hashing`: the hashing trick, for large-vocabulary categorical features
    *   `Discretization`: turn continuous numerical features into categorical
        features by binning their values

* Allow having empty paths in *path operations* used with `include_router` and a `prefix`.
    * This allows having a router for `/cats` and all its *path operations*, while having one of them for `/cats`.
    * Now it doesn't have to be only `/cats/` (with a trailing slash).

testingOnlyRejection func() // Signature is an ECDSA signature, where r and s are represented as big-endian // byte slices of the same length as the curve order. type Signature struct { R, S []byte } // Sign signs a hash (which shall be the result of hashing a larger message with // the hash function H) using the private key, priv. If the hash is longer than // the bit-length of the private key's curve order, the hash will be truncated // to that length. func Sign[P Point[P], H fips140.Hash](c *Curve[P],...

testingOnlyRejection func() // Signature is an ECDSA signature, where r and s are represented as big-endian // byte slices of the same length as the curve order. type Signature struct { R, S []byte } // Sign signs a hash (which shall be the result of hashing a larger message with // the hash function H) using the private key, priv. If the hash is longer than // the bit-length of the private key's curve order, the hash will be truncated // to that length. func Sign[P Point[P], H hash.Hash](c *Curve[P],...