chore: add room configs back in

At the moment, MC relies on some of these classes, so they are necessary
in Essentials for now. We can explore how to remove them at a later date

src/PepperDash.Essentials.Core/Room/Config/EssentialsHuddleVtc1PropertiesConfig.cs

@@ -0,0 +1,13 @@
+
+using Newtonsoft.Json;
+
+namespace PDT.Plugins.Essentials.Rooms.Config
+{
+
+    public class EssentialsHuddleVtc1PropertiesConfig : EssentialsConferenceRoomPropertiesConfig
+    {
+		[JsonProperty("defaultDisplayKey")]
+		public string DefaultDisplayKey { get; set; }
+
+    }
+}