Upgrade to C++23

[Ataba29]

We are using c++17, which is pretty old and with C++26 around the corner I would rather upgrade now and get the project refactored ahead of the newest version coming out rather than keep it at 17, another major upgrade is threading which can be written better.

[Ataba29]

• Didn't write this in the first comment, but there is a thing called jthread that we can take advantage of, which was introduced in C++20
• Also, the project needs refactoring when it comes to functions putting public first, private second, and renaming Server.h private variables