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.

src/__Libraries/StellaOps.Microservice.SourceGen/DiagnosticDescriptors.cs

@@ -0,0 +1,55 @@
+using Microsoft.CodeAnalysis;
+
+namespace StellaOps.Microservice.SourceGen;
+
+/// <summary>
+/// Diagnostic descriptors for the source generator.
+/// </summary>
+internal static class DiagnosticDescriptors
+{
+    private const string Category = "StellaOps.Microservice";
+
+    /// <summary>
+    /// Class with [StellaEndpoint] must implement IStellaEndpoint or IRawStellaEndpoint.
+    /// </summary>
+    public static readonly DiagnosticDescriptor MissingHandlerInterface = new(
+        id: "STELLA001",
+        title: "Missing handler interface",
+        messageFormat: "Class '{0}' with [StellaEndpoint] must implement IStellaEndpoint<TRequest, TResponse> or IRawStellaEndpoint",
+        category: Category,
+        defaultSeverity: DiagnosticSeverity.Error,
+        isEnabledByDefault: true);
+
+    /// <summary>
+    /// Duplicate endpoint detected.
+    /// </summary>
+    public static readonly DiagnosticDescriptor DuplicateEndpoint = new(
+        id: "STELLA002",
+        title: "Duplicate endpoint",
+        messageFormat: "Duplicate endpoint: {0} {1} is defined in both '{2}' and '{3}'",
+        category: Category,
+        defaultSeverity: DiagnosticSeverity.Warning,
+        isEnabledByDefault: true);
+
+    /// <summary>
+    /// [StellaEndpoint] on abstract class is ignored.
+    /// </summary>
+    public static readonly DiagnosticDescriptor AbstractClassIgnored = new(
+        id: "STELLA003",
+        title: "Abstract class ignored",
+        messageFormat: "[StellaEndpoint] on abstract class '{0}' is ignored",
+        category: Category,
+        defaultSeverity: DiagnosticSeverity.Warning,
+        isEnabledByDefault: true);
+
+    /// <summary>
+    /// Informational: endpoints generated.
+    /// </summary>
+    public static readonly DiagnosticDescriptor EndpointsGenerated = new(
+        id: "STELLA004",
+        title: "Endpoints generated",
+        messageFormat: "Generated {0} endpoint descriptors",
+        category: Category,
+        defaultSeverity: DiagnosticSeverity.Info,
+        isEnabledByDefault: false);
+}