feat: add IHasDestinationList and IHasSourceList interfaces for room management

src/PepperDash.Essentials.Core/Room/IHasDestinationList.cs

@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+using PepperDash.Essentials.Core;
+
+
+/// <summary>
+/// Interface for rooms with a list of destinations
+/// </summary>
+interface IHasDestinationList
+{
+    /// <summary>
+    /// Gets the dictionary of destinations.
+    /// </summary>
+    Dictionary<string, IRoutingSink> Destinations { get; }
+}