WIP: Add public/get_last_trades_by_currency method, allow for pagination results

[OskarGottlieb]

Ok, so I was playing around with your library some more, tried to add the get_last_trades_by_currency method, but that didn't work on its own, as the "result" part of the json response actually has two parts - "trades" which has the collection of trades and has_more which is a bool.
Couldn't parse it w/ the existing helper enum, so had to write an object that wraps around Either..which uhm I don't like? I mean it works, I was able to make it run, but I'd say I'm still new-ish to Rust and it just isn't a solution I like right out of the gate, hence the WIP.

If I'm reading it correctly, Either is really the same object collections crate uses that you're using here so you can parse either the response or an error and propagate it back to the user?
Also I couldn't figure out what's the purpose of Any enums, looks like it's dead code? Thanks for writing this library, I think I'm getting the gist of the internals and I definitely learned a lot by reading the code and playing around w/ it!

[dovahcrow]

I think here you can make GetLastTradesByCurrencyResponse into

struct GetLastTradesByCurrencyResponse {
    trades: Vec<LastTrade>,
    has_more: bool
}

and in impl Request it can have

type Response =GetLastTradesByCurrencyResponse;

then

struct LastTrade {
  pub amount: Option<f64>,
    pub block_trade_id: Option<String>,
    pub direction: Direction,
    pub index_price: f64,
    pub instrument_name: String,
    pub iv: Option<f64>,
    pub mark_price: f64,
    pub price: f64,
    pub trade_id: String,
    pub timestamp: u64,
    pub trade_seq: u64,
    pub tick_direction: i64,
}