engine/exchanges: Add GetCurrencyTradeURL wrapper func/gRPC endpoint (#1521)

* beginning the concept

* expands testing and implementations

* test standardisation, expansion

* more

* finish remainder, add rpc func

* lint

* grammar? I barely know her!

* wow i forgot something wow wow wow wow

* rm SendPayload

* enFixio!

* improve binance long-dated support

* update test design, update wrapper funcs

* adds kraken futures, adds bybit support

* fixes SIMPLE bugs

* s is for sucks

* fixed option url x2

* fixed silly test

engine/rpcserver.go

@@ -6016,3 +6016,36 @@ func (s *RPCServer) GetOpenInterest(ctx context.Context, r *gctrpc.GetOpenIntere
 		Data: resp,
 	}, nil
 }
+
+// GetCurrencyTradeURL returns the URL for the trading pair
+func (s *RPCServer) GetCurrencyTradeURL(ctx context.Context, r *gctrpc.GetCurrencyTradeURLRequest) (*gctrpc.GetCurrencyTradeURLResponse, error) {
+	if r == nil {
+		return nil, fmt.Errorf("%w GetCurrencyTradeURLRequest", common.ErrNilPointer)
+	}
+	exch, err := s.GetExchangeByName(r.Exchange)
+	if err != nil {
+		return nil, err
+	}
+	if !exch.IsEnabled() {
+		return nil, fmt.Errorf("%s %w", r.Exchange, errExchangeNotEnabled)
+	}
+	ai, err := asset.New(r.Asset)
+	if err != nil {
+		return nil, err
+	}
+	if r.Pair == nil ||
+		(r.Pair.Base == "" && r.Pair.Quote == "") {
+		return nil, currency.ErrCurrencyPairEmpty
+	}
+	cp, err := exch.MatchSymbolWithAvailablePairs(r.Pair.Base+r.Pair.Quote, ai, false)
+	if err != nil {
+		return nil, err
+	}
+	url, err := exch.GetCurrencyTradeURL(ctx, ai, cp)
+	if err != nil {
+		return nil, err
+	}
+	return &gctrpc.GetCurrencyTradeURLResponse{
+		Url: url,
+	}, nil
+}