Implement the LID

[jmg-duarte]

Description

This PR implements the LID component (currently, without the JSON-RPC) which supersedes the piecestore.

Fixes #33

Important points for reviewers

I've "over documented" the code with references back to the original code to shorten the time it takes for one to learn about the details and reasons behind certain choices being made.

There are some places were I've deviated from the original implementation, but hopefully those are sensible enough.

Checklist

• Are there important points that reviewers should know?
• Make sure that you described what this change does.
• If there are follow-ups, have you created issues for them?
  • If yes, which ones? / List them here
• Have you tested this solution?
• Were there any alternative implementations considered?
• Did you document new (or modified) APIs?

[th7nder]

I'm a bit confused which parts were already there, which are new and what was changed. I was trying to read it all, but gave up in the middle of rdb.rs.
Should we separate the implementation of the Service trait somewhere, so we know what to look at? Maybe leave piecestore by and only add the Service trait, have the refactor in a separate PR?
As well, are the tests covering the new Service trait, or are they old ones?
Should we add some kind of integration tests?

By the way, it looks like a huuuge piece of work with a lots of quirks and twists that you needed to parse and implement.
It's a pleasure to try to understand and read engineering done like that!

[th7nder]

Hell of a job!
We established that integration tests will come later, when we add the RPC layer.
I digged through all of the code, don't see anything worth debating now.
If we see something wrong in the upper layers, then we'll fix it.
Let's go!

[cernicc]

Great work 💪

[serg-temchenko]

Looks great! 🔥 💪