Wow! It looks very interesting! Congrats!
After a fast review of the documentation, here are some thoughts:

• Pros:

  • Available in brew
  • Nicely documented. Complete and to the point.
  • Code is very readable.
  • Good MVP scope.

• Potential improvement

  • I’d consider providing it as a Conan and/or Vcpkg package
  • What is the minimum C++ version? C++17? C++20?
  • If it is C++20, I’d consider using reflection for serialization. And regarding the friend functions, still, not convinced that private data should be serialized.
    Keep up the great work!
    Best regards,

  Jorge