Add unit tests for Router configuration and transport layers

- Implemented tests for RouterConfig, RoutingOptions, StaticInstanceConfig, and RouterConfigOptions to ensure default values are set correctly.
- Added tests for RouterConfigProvider to validate configurations and ensure defaults are returned when no file is specified.
- Created tests for ConfigValidationResult to check success and error scenarios.
- Developed tests for ServiceCollectionExtensions to verify service registration for RouterConfig.
- Introduced UdpTransportTests to validate serialization, connection, request-response, and error handling in UDP transport.
- Added scripts for signing authority gaps and hashing DevPortal SDK snippets.

examples/router/tests/Examples.Integration.Tests/BillingEndpointTests.cs

@@ -0,0 +1,76 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text;
+using System.Text.Json;
+using FluentAssertions;
+using Xunit;
+
+namespace Examples.Integration.Tests;
+
+/// <summary>
+/// Integration tests for the Billing microservice endpoints.
+/// </summary>
+public sealed class BillingEndpointTests : IClassFixture<GatewayFixture>
+{
+    private readonly GatewayFixture _fixture;
+
+    public BillingEndpointTests(GatewayFixture fixture)
+    {
+        _fixture = fixture;
+    }
+
+    [Fact]
+    public async Task CreateInvoice_WithValidRequest_ReturnsCreatedInvoice()
+    {
+        // Arrange
+        var request = new
+        {
+            customerId = "CUST-001",
+            amount = 99.99m,
+            description = "Test invoice"
+        };
+
+        // Act
+        var response = await _fixture.GatewayClient.PostAsJsonAsync("/invoices", request);
+
+        // Assert
+        response.StatusCode.Should().Be(HttpStatusCode.OK);
+        var content = await response.Content.ReadAsStringAsync();
+        content.Should().Contain("invoiceId");
+    }
+
+    [Fact]
+    public async Task GetInvoice_WithValidId_ReturnsInvoice()
+    {
+        // Arrange
+        var invoiceId = "INV-12345";
+
+        // Act
+        var response = await _fixture.GatewayClient.GetAsync($"/invoices/{invoiceId}");
+
+        // Assert
+        response.StatusCode.Should().Be(HttpStatusCode.OK);
+        var content = await response.Content.ReadAsStringAsync();
+        content.Should().Contain(invoiceId);
+    }
+
+    [Fact]
+    public async Task UploadAttachment_WithStreamingData_ReturnsSuccess()
+    {
+        // Arrange
+        var invoiceId = "INV-12345";
+        var attachmentData = Encoding.UTF8.GetBytes("This is test attachment content");
+        using var content = new ByteArrayContent(attachmentData);
+        content.Headers.ContentType = new System.Net.Http.Headers.MediaTypeHeaderValue("application/octet-stream");
+
+        // Act
+        var response = await _fixture.GatewayClient.PostAsync(
+            $"/invoices/{invoiceId}/attachments",
+            content);
+
+        // Assert
+        response.StatusCode.Should().Be(HttpStatusCode.OK);
+        var responseContent = await response.Content.ReadAsStringAsync();
+        responseContent.Should().Contain("attachmentId");
+    }
+}