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/ValidationProblemDetails.cs

@@ -0,0 +1,101 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace StellaOps.Microservice.Validation;
+
+/// <summary>
+/// RFC 7807 Problem Details for schema validation failures.
+/// Returns HTTP 422 Unprocessable Entity.
+/// </summary>
+public sealed class ValidationProblemDetails
+{
+    private static readonly JsonSerializerOptions SerializerOptions = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.CamelCase,
+        DefaultIgnoreCondition = JsonIgnoreCondition.WhenWritingNull
+    };
+
+    /// <summary>
+    /// A URI reference identifying the problem type.
+    /// </summary>
+    [JsonPropertyName("type")]
+    public string Type { get; init; } = "https://stellaops.io/errors/schema-validation";
+
+    /// <summary>
+    /// A short, human-readable summary of the problem.
+    /// </summary>
+    [JsonPropertyName("title")]
+    public string Title { get; init; } = "Schema Validation Failed";
+
+    /// <summary>
+    /// The HTTP status code (422).
+    /// </summary>
+    [JsonPropertyName("status")]
+    public int Status { get; init; } = 422;
+
+    /// <summary>
+    /// A human-readable explanation specific to this occurrence.
+    /// </summary>
+    [JsonPropertyName("detail")]
+    public string? Detail { get; init; }
+
+    /// <summary>
+    /// A URI reference identifying the specific occurrence (the endpoint path).
+    /// </summary>
+    [JsonPropertyName("instance")]
+    public string? Instance { get; init; }
+
+    /// <summary>
+    /// The trace/correlation ID for distributed tracing.
+    /// </summary>
+    [JsonPropertyName("traceId")]
+    public string? TraceId { get; init; }
+
+    /// <summary>
+    /// The list of validation errors.
+    /// </summary>
+    [JsonPropertyName("errors")]
+    public IReadOnlyList<SchemaValidationError> Errors { get; init; } = [];
+
+    /// <summary>
+    /// Creates a ValidationProblemDetails for schema validation failures.
+    /// </summary>
+    /// <param name="method">The HTTP method.</param>
+    /// <param name="path">The endpoint path.</param>
+    /// <param name="direction">Request or response validation.</param>
+    /// <param name="errors">The validation errors.</param>
+    /// <param name="correlationId">Optional correlation ID.</param>
+    public static ValidationProblemDetails Create(
+        string method,
+        string path,
+        SchemaDirection direction,
+        IReadOnlyList<SchemaValidationError> errors,
+        string? correlationId = null)
+    {
+        var directionText = direction == SchemaDirection.Request ? "request" : "response";
+        return new ValidationProblemDetails
+        {
+            Detail = $"{char.ToUpperInvariant(directionText[0])}{directionText[1..]} body failed schema validation for {method} {path}",
+            Instance = path,
+            TraceId = correlationId,
+            Errors = errors
+        };
+    }
+
+    /// <summary>
+    /// Converts this problem details to a RawResponse.
+    /// </summary>
+    public RawResponse ToRawResponse()
+    {
+        var json = JsonSerializer.SerializeToUtf8Bytes(this, SerializerOptions);
+        var headers = new HeaderCollection();
+        headers.Set("Content-Type", "application/problem+json; charset=utf-8");
+
+        return new RawResponse
+        {
+            StatusCode = Status,
+            Headers = headers,
+            Body = new MemoryStream(json)
+        };
+    }
+}