Bounds checking silently disabled on unrecognized containers

[gregmarr]

For range checking on containers, if any of size(container) or ssize(container) or .begin(container) + 2 don't work, then the CPP2_ASSERT_IN_BOUNDS checking is silently disabled. It seems like for maximum safety, the user should have to either make the container meet the requirements or explicitly opt out using some mechanism like this for cpp1 containers:

constexpr template<> auto allow_unchecked_bounds_access<MyContainer>() -> std::true_type { return {} };

or some other decoration, perhaps a metaclass, or unsafe on the operator[], for cpp2 containers.