[FIX] [Bitfinex] Fixed market symbol separator (#699) (#707)

Author: MatheusKlauck

src/ExchangeSharp/API/Exchanges/Bitfinex/ExchangeBitfinexAPI.cs

@@ -62,7 +62,7 @@ private ExchangeBitfinexAPI()
 				["ZEC"] = "zcash",
 			};
 
-			MarketSymbolSeparator = string.Empty;
+			MarketSymbolSeparator = ":";
 		}
 
 		public override string PeriodSecondsToString(int seconds)

tests/ExchangeSharpTests/ExchangeBitfinexTests.cs

@@ -14,6 +14,8 @@ The above copyright notice and this permission notice shall be included in all c
 using ExchangeSharp;
 using System.Net;
 using System.Security;
+using System;
+using FluentAssertions;
 
 namespace ExchangeSharpTests
 {
@@ -40,5 +42,16 @@ public void SubmitStopMarginOrder()
 			api.PublicApiKey = _pubKey;
 			ExchangeOrderResult result = api.PlaceOrderAsync(order).Result;
 		}
+
+		[TestMethod]
+		public void GetDataFromMarketWithSpecialChar()
+		{
+			IExchangeAPI api = ExchangeAPI.GetExchangeAPIAsync("Bitfinex").Result;
+			string marketTicker = "DOGE:USD";
+			DateTime start = new DateTime(2021, 12, 1);
+			DateTime end = DateTime.Today;
+			System.Collections.Generic.IEnumerable<MarketCandle> result = api.GetCandlesAsync(marketTicker, 86400, start, end, 1000).Result;
+			result.Should().HaveCountGreaterThan(0, "Returned data");
+		}
 	}
 }