exchanges/websocket: Expose Trades/Fills feed through data channel (#814)

* Expose trade feed websocket exchange data through data channel

Most relevant to applications that import GCT as a lib, this allows
them to (through configuration, disabled by default) receive trade data
through the data channel similarly to the orderbook feed.

* exchanges: allow exposure of trade websocket feed through data channel

* Expose fill feed websocket abstracted exchange data through data channel

* exchanges: allow exposure of fill websocket feed through data channel

exchanges/stream/websocket.go

@@ -145,11 +145,22 @@ func (w *Websocket) Setup(s *WebsocketSetup) error {
 	w.Wg = new(sync.WaitGroup)
 	w.SetCanUseAuthenticatedEndpoints(s.ExchangeConfig.API.AuthenticatedWebsocketSupport)
 
-	return w.Orderbook.Setup(s.ExchangeConfig,
+	if err := w.Orderbook.Setup(s.ExchangeConfig,
 		s.SortBuffer,
 		s.SortBufferByUpdateIDs,
 		s.UpdateEntriesByID,
+		w.DataHandler); err != nil {
+		return err
+	}
+
+	w.Trade.Setup(w.exchangeName,
+		s.TradeFeed,
 		w.DataHandler)
+
+	w.Fills.Setup(s.FillsFeed,
+		w.DataHandler)
+
+	return nil
 }
 
 // SetupNewConnection sets up an auth or unauth streaming connection

exchanges/stream/websocket_types.go

@@ -6,8 +6,10 @@ import (
 
 	"github.com/gorilla/websocket"
 	"github.com/thrasher-corp/gocryptotrader/config"
+	"github.com/thrasher-corp/gocryptotrader/exchanges/fill"
 	"github.com/thrasher-corp/gocryptotrader/exchanges/protocol"
 	"github.com/thrasher-corp/gocryptotrader/exchanges/stream/buffer"
+	"github.com/thrasher-corp/gocryptotrader/exchanges/trade"
 )
 
 // Websocket functionality list and state consts
@@ -72,6 +74,12 @@ type Websocket struct {
 	// Orderbook is a local buffer of orderbooks
 	Orderbook buffer.Orderbook
 
+	// Trade is a notifier of occurring trades
+	Trade trade.Trade
+
+	// Fills is a notifier of occurring fills
+	Fills fill.Fills
+
 	// trafficAlert monitors if there is a halt in traffic throughput
 	TrafficAlert chan struct{}
 	// ReadMessageErrors will received all errors from ws.ReadMessage() and
@@ -100,6 +108,9 @@ type WebsocketSetup struct {
 	SortBuffer            bool
 	SortBufferByUpdateIDs bool
 	UpdateEntriesByID     bool
+	TradeFeed             bool
+	// Fill data config values
+	FillsFeed bool
 }
 
 // WebsocketConnection contains all the data needed to send a message to a WS