span constructor improvements

[BurningEnlightenment]

stduuid/include/uuid.h

Line 402 in 3afe719

explicit uuid(span<value_type, 16> bytes)

This should be changed to

explicit uuid(span<value_type const, 16> bytes) 

in order to support construction from immutable contiguous containers and it can be made constexpr in C++20 mode.

It would also be nice if we had a

CONSTEXPR20 explicit uuid(span<std::byte const, 16> bytes) 

constructor for symmetry with as_bytes() -> span<std::byte const, 16> bytes.

I'd be willing to implement it and update the paper if this is uncontroversial.

[mcopik]

👍 for the problem - the interface is right now inconsistent. as_bytes uses std::byte while creating a new uuid enforce casting to uint8_t.