Add overloads for working with capy/corosio

[R-Goc]

When trying to write a simple server, I noticed that when writing to a corosio tcp_socket creating the const buffer for the write is rather ugly. Since these libraries are already so tied together methods/overloads for working with capy/corosio would be nice. For example this:

        http::response res;
        res.set_status(http::status::ok);
        auto [ec, n] = co_await m_socket.write_some(
            capy::const_buffer{res.buffer().data(), res.buffer().size()});

Unless I missed some very obvious method, there is no nice way to pass an http::request to write_some. Just .buffer() doesn't work as write_some doesn't accept a string_view.

[vinniefalco]

Yes there is friction here that needs addressing. How does ASIO do it?

[R-Goc]

Not too familiar with ASIO. Const_buffer in asio has a constructor that accepts a span. I assume string_view would satisfy this from looking at it but I didn't try. https://think-async.com/Asio/asio-1.38.2/doc/asio/reference/const_buffer/const_buffer/overload4.html