cista_members() approach: serialize tuples properly

[AdelKS]

Hello!

While migrating code to the new approach, here's something that seems to not be handled properly with the new approach:

struct A
{
  std::tuple<std::tuple<int, int>, int> vals;

  A() : vals({ {1, 2}, 3}) {}

  auto cista_members()
  {
    return std::tie(vals);
  }
};

int main()
{
  A a;
  cista::byte_buf buffer = cista::serialize(a);
  return 0
}

[felixguendling]

Using cista::tuple instead of std::tuple works.

[AdelKS]

Oh it's again a matter of supporting STL containers I suppose, alright thanks !