traitify client

[gnunicorn]

the Client from sc-client is a massive pull-it-all-together within the outer substrate infrastructure. While many features already depend on specific traits rather than the client directly, the client still has a few functions exclusive to it, that some other crates depend on, but some also depend on client without actually needing these functions. The goal is to make nothing in sc-* depend on client directly anymore and move client into the internals of sc-service.

The way forward is probably (in this order):

• remove Client<..> dependencies where other traits are defining the use API well enough already
• create proper traits for remaining functionality in Client in sc-api
• replace remaining Client-dependencies with dependencies on sc-api
• move Client into sc-service, make it internal–this probably needs some tweaking for tests (see test-client)
• drop sc-client

This is an evolved refactor that probably has to touch a lot of (internal) code and where-clauses. Rust experience is required. Expect this to take a while. I am happy to mentor.

[seunlanlege]

@gnunicorn Interested in picking this up.