chore: import upstream snapshot with attribution

Algorithm/Risk/NullRiskManagementModel.cs

@@ -0,0 +1,22 @@
+using System.Collections.Generic;
+using System.Linq;
+using QuantConnect.Algorithm.Framework.Portfolio;
+
+namespace QuantConnect.Algorithm.Framework.Risk
+{
+    /// <summary>
+    /// Provides an implementation of <see cref="IRiskManagementModel"/> that does nothing
+    /// </summary>
+    public class NullRiskManagementModel : RiskManagementModel
+    {
+        /// <summary>
+        /// Manages the algorithm's risk at each time step
+        /// </summary>
+        /// <param name="algorithm">The algorithm instance</param>
+        /// <param name="targets">The current portfolio targets to be assessed for risk</param>
+        public override IEnumerable<IPortfolioTarget> ManageRisk(QCAlgorithm algorithm, IPortfolioTarget[] targets)
+        {
+            return Enumerable.Empty<IPortfolioTarget>();
+        }
+    }
+}