Extensible Ouroboros Network Diffusion Stack

[bolt12]

Description

This PR refactors ouroboros-network in order to make diffusion layer general/polymorphic and extensible. This will allow us (or 3rd parties) to have access to a flexible network stack which can be extended/configured to ones needs.

For more details about this refactoring, see https://github.com/IntersectMBO/ouroboros-network/wiki/Reusable-Diffusion-Investigation

TODOs:

• Better document PRP invariants and refactor/cleanup insertion functions
• remove daBlockFetchMode
• Consensus uses a entirely different project for Cardano Node consensus layer instantiation, decide what's the best approach for the networking code.

For next steps (e,.g. when developing mithril) this will be in the todo list:

• Add tests for the general components: Churn, OG, etc..
• Generalise peerChurnGovernor to only have one implementation and not 2
• Redesign bootstrap peers as a concept to be general enough to be usable by third party users. Right now it is very cardano-node specific.
• Create a sub library that holds all cardano-node specific types and functions, this will be better for organising dependencies and the code overall
• Move Cardano specific things from cardano-node, we should think of moving some of the other things to ouroboros-network as well, e.g. topology file format for example. 3rd parties don't need to reimplement it from scratch.

[yihuang]

a step toward haskell blockchain sdk? 😄

[bolt12]

@yihuang as you can see from the PR description this is some interesting step towards a fully polymorphic diffusion that might be used by others to create their own overlay network! Thank you for noticing 😃

[coot]

I reviewed the first two patches:

git hash	commit title
bae4f75	Pull out Cardano specifics to different modules
cb0da21	Add extension points to Diffusion data structures

[coot]

LGTM

[coot]

Approved