Coordination service API in YDB Rust SDK

PR: ydb-rs-sdk/pull/162

To leverage async Rust skills, I joined a semester project to implement a client and SDK API for the YDB Coordination service inside its Rust SDK.

The main challenge was to implement a Semaphore API. The distributed locking problem is hard in terms of guarantees and SDK ergonomics:

You can read the following articles:

• Martin Kleppmann: “How to do distributed locking”
• “etcd versus other key-value stores”

I’ve implemented the API, which allowed implementing Leader election, Service discovery and Resource limiting using YDB and Rust.