Agent Trait

[abezukor]

Uses a trait for registering agents as IMO it is much more idiomatic then manually creating a

pub type RequestPassPhraseFn = Box<
    dyn (Fn() -> Pin<Box<dyn Future<Output = Result<String, Box<dyn std::error::Error>>> + Send>>)
        + Send
        + Sync,
>;

For completeness, I have also added the other possible methods to the agent trait.

[pythops]

let's break it down into separate PR. that way it will be much easier to review :)

[abezukor]

@pythops I broke the PR up (see #7). Any other comments?

[pythops]

I will review all your PRs on Friday, busy these days with work sorry

[pythops]

Excellent !