Override GetBuyingPowerModel to support USDC collaterla in dYdX brokerage

Author: AdalyatNazirov

Common/Brokerages/dYdXBrokerageModel.cs

@@ -43,6 +43,21 @@ public dYdXBrokerageModel(AccountType accountType = AccountType.Margin) : base(a
         }
     }
 
+    /// <summary>
+    /// Gets a new buying power model for the security, returning the default model with the security's configured leverage.
+    /// For cash accounts, leverage = 1 is used.
+    /// </summary>
+    /// <param name="security">The security to get a buying power model for</param>
+    /// <returns>The buying power model for this brokerage/security</returns>
+    public override IBuyingPowerModel GetBuyingPowerModel(Security security)
+    {
+        return security?.Type switch
+        {
+            SecurityType.CryptoFuture => new SecurityMarginModel(GetLeverage(security)),
+            _ => base.GetBuyingPowerModel(security)
+        };
+    }
+
     /// <summary>
     /// Provides dYdX fee model
     /// </summary>
@@ -145,4 +160,4 @@ private static IReadOnlyDictionary<SecurityType, string> GetDefaultMarkets(strin
         map[SecurityType.CryptoFuture] = marketName;
         return map.ToReadOnlyDictionary();
     }
-}
+}