Feature: download specification (#18)

* feat: parameterless ctor in downloader

* feat: json specification

QuantConnect.OandaBrokerage.ToolBox/OandaDataDownloader.cs

@@ -19,6 +19,7 @@
 using NodaTime;
 using QuantConnect.Data;
 using QuantConnect.Data.Market;
+using QuantConnect.Configuration;
 using QuantConnect.Brokerages.Oanda;
 using QuantConnect.Util;
 using Environment = QuantConnect.Brokerages.Oanda.Environment;
@@ -33,6 +34,9 @@ public class OandaDataDownloader : IDataDownloader
         private readonly OandaBrokerage _brokerage;
         private readonly OandaSymbolMapper _symbolMapper = new OandaSymbolMapper();
 
+        public OandaDataDownloader() : this(Config.Get("oanda-access-token"), Config.Get("oanda-account-id"))
+        { }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="OandaDataDownloader"/> class
         /// </summary>

oanda.json

@@ -13,5 +13,24 @@
 	"order-types": [ "Market", "Limit", "Stop Market" ],
 	"assets": ["Forex", "CFD"], 
 	"brokerage-url": "https://www.oanda.com/",
-	"documentation": "/docs/v2/cloud-platform/live-trading/brokerages/oanda"
+	"documentation": "/docs/v2/cloud-platform/live-trading/brokerages/oanda",
+	"module-specification": {
+        "download": {
+            "data-types": [
+                "Quote"
+            ],
+            "resolutions": [
+                "Second",
+                "Minute",
+                "Hour",
+                "Daily"
+            ],
+            "security-types": [
+				"Forex"
+            ],
+            "markets": [
+                "Oanda"
+            ]
+        }
+    }
 }