std::byte support

[Trafo]

Hi,

from my perspective, the way to go for the future is to support std::byte as a native byte type. But Botan actually makes it hard to use std::byte. One of the most critical parts is actually this requirement of secure_alloacator:

template <typename T>
#if !defined(_ITERATOR_DEBUG_LEVEL) || _ITERATOR_DEBUG_LEVEL == 0
/*
  * Assert exists to prevent someone from doing something that will
  * probably crash anyway (like secure_vector<non_POD_t> where ~non_POD_t
  * deletes a member pointer which was zeroed before it ran).
  * MSVC in debug mode uses non-integral proxy types in container types
  * like std::vector, thus we disable the check there.
 */
   requires std::is_integral<T>::value
#endif

It is still Botan 2 because Botan 3 still does not have a conan recipe. But I would at least allow the std::byte type here. In the long run, it will be very beneficial as well, that the implementer can use the API with std::byte as well.

Best regards, Trafo

[EDIT] But in general awesome work. If there were std::byte support in general, it would be super easy and modern to use crypto lib, which gives many possibilities. Could we just replace std::uint8_t with a botan_byte? Where implementers can define if they want std::byte or for legacy reasons std::uint8_t?