...one of the most highly
regarded and expertly designed C++ library projects in the
world.
— Herb Sutter and Andrei
Alexandrescu, C++
Coding Standards
The type for each element in the list of buffers.
using value_type = see-below;
If BufferSequence meets the requirements of MutableBufferSequence,
then this type will be net::mutable_buffer
,
otherwise this type will be net::const_buffer
.