Extract the client core out into native libraries, that the API that users use will wrap

[mieubrisse]

This way, we only write & test the core logic once, and then all the Python/Go/Java/etc clienits just call down to the native code

This also gives us the ability to version API-calling code in the client in Core, so that we don't get into this weird dependency loop where Core depends on Go depends on Core

[mieubrisse]

Done by pushing the logic inside Kurt API, alhamdulilah