Is there any documentation/tutorials covering the technical details behind the Polkadot relay chain source code, specifically the runtime where all the special logic of the relay chain occurs? I am referring to the code in this repo: https://github.com/paritytech/polkadot. So far, the tutorials I have found mainly deal with creating new blockchains with Substrate.
For instance, if I was trying to change the relay chain such that parachains don't need to be auctioned off and can only be used by people with the admin (sudo) key, I would need to understand how the relay chain source code works and is organized. Any resources are greatly appreciated!