Implement worker MXAccess event queue

src/MxGateway.Worker/MxAccess/MxAccessEventQueueOverflowException.cs

@@ -0,0 +1,14 @@
+using System;
+
+namespace MxGateway.Worker.MxAccess;
+
+public sealed class MxAccessEventQueueOverflowException : Exception
+{
+    public MxAccessEventQueueOverflowException(int capacity)
+        : base($"MXAccess outbound event queue reached its configured capacity of {capacity}.")
+    {
+        Capacity = capacity;
+    }
+
+    public int Capacity { get; }
+}