The configuration of the fetch process was only achieved at the setup
of the of the node.
This limits the ability to pass configuration options to the fetch
worker while the node service is running.
This change introduces `radicle_protocol::fetcher::state::FetchConfig`
to allow configuration options to be kept track of. This includes the
previous `timeout` option, but now also includes the
`radicle_fetch::Config`.
The service now produces the `FetchConfig` and passes it through to
the fetch worker.
Using empty `Vec`s to mean "all refs" can be confusing. Avoid the chance
of confusion by introduction of a new type that clearly describes which
refs should be fetched.
This patch introduces the `FetcherState` which encapsulates the logic
and state for keeping track of fetches.
It uses a sans-IO approach, where the state of fetches transition
based on the current state and provided input.
Callers can then decide to perform I/O based on the returned event.
Fintan Halpenny
Lorenz Leutgeb