Add unit tests for RabbitMq and Udp transport servers and clients

- Implemented comprehensive unit tests for RabbitMqTransportServer, covering constructor, disposal, connection management, event handlers, and exception handling.
- Added configuration tests for RabbitMqTransportServer to validate SSL, durable queues, auto-recovery, and custom virtual host options.
- Created unit tests for UdpFrameProtocol, including frame parsing and serialization, header size validation, and round-trip data preservation.
- Developed tests for UdpTransportClient, focusing on connection handling, event subscriptions, and exception scenarios.
- Established tests for UdpTransportServer, ensuring proper start/stop behavior, connection state management, and event handling.
- Included tests for UdpTransportOptions to verify default values and modification capabilities.
- Enhanced service registration tests for Udp transport services in the dependency injection container.

src/__Libraries/StellaOps.Microservice/Validation/SchemaValidationException.cs

@@ -0,0 +1,53 @@
+namespace StellaOps.Microservice.Validation;
+
+/// <summary>
+/// Exception thrown when request or response body fails schema validation.
+/// </summary>
+public sealed class SchemaValidationException : Exception
+{
+    /// <summary>
+    /// Gets the endpoint path where validation failed.
+    /// </summary>
+    public string EndpointPath { get; }
+
+    /// <summary>
+    /// Gets the HTTP method of the endpoint.
+    /// </summary>
+    public string EndpointMethod { get; }
+
+    /// <summary>
+    /// Gets whether this was request or response validation.
+    /// </summary>
+    public SchemaDirection Direction { get; }
+
+    /// <summary>
+    /// Gets the list of validation errors.
+    /// </summary>
+    public IReadOnlyList<SchemaValidationError> Errors { get; }
+
+    /// <summary>
+    /// Creates a new schema validation exception.
+    /// </summary>
+    public SchemaValidationException(
+        string endpointMethod,
+        string endpointPath,
+        SchemaDirection direction,
+        IReadOnlyList<SchemaValidationError> errors)
+        : base(BuildMessage(endpointMethod, endpointPath, direction, errors))
+    {
+        EndpointMethod = endpointMethod;
+        EndpointPath = endpointPath;
+        Direction = direction;
+        Errors = errors;
+    }
+
+    private static string BuildMessage(
+        string method,
+        string path,
+        SchemaDirection direction,
+        IReadOnlyList<SchemaValidationError> errors)
+    {
+        var directionText = direction == SchemaDirection.Request ? "request" : "response";
+        return $"Schema validation failed for {directionText} of {method} {path}: {errors.Count} error(s)";
+    }
+}