nanorpc: magic library for a JSON-RPC 2.0 subset (WIP)

nanorpc implements a subset of JSON-RPC 2.0, notably with the lack of no-response "notifications" and lack of negative-value error codes.

The most interesting part of nanorpc is that it contains a derive macro, #[nanorpc], that given a trait that describes the server-side behavior of an RPC service, derives both raw JSON-RPC handlers and a client implementation:

#[nanorpc_derive]
#[async_trait]
pub trait MathProtocol {
    /// Adds two numbers
    async fn add(&self, x: f64, y: f64) -> f64;
    /// Multiplies two numbers
    async fn mult(&self, x: f64, y: f64) -> f64;
}

// Autogenerates a server struct:
pub struct MathService<T: MathProtocol>(pub T);

#[async_trait]
impl <T: MathService> RpcService for MathService<T> {
    //...
}

// Autogenerates a client struct like:

pub struct MathClient<T: RpcTransport>(pub T);

impl <T: RpcTransport> MathClient {
    /// Adds two numbers
    pub async fn add(&self, x: f64, y: f64) -> Result<f64, T::Error>;

    //...
}

Note: right now the library is NOT done. Do not attempt to use it yet, the above is just a sketch of what it will do.