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.Router.Transport.Tls/CertificateLoader.cs

@@ -0,0 +1,104 @@
+using System.Security.Cryptography.X509Certificates;
+
+namespace StellaOps.Router.Transport.Tls;
+
+/// <summary>
+/// Utility class for loading certificates from various sources.
+/// </summary>
+public static class CertificateLoader
+{
+    /// <summary>
+    /// Loads a server certificate from the options.
+    /// </summary>
+    /// <param name="options">The TLS transport options.</param>
+    /// <returns>The loaded certificate.</returns>
+    /// <exception cref="InvalidOperationException">Thrown when no certificate is configured.</exception>
+    public static X509Certificate2 LoadServerCertificate(TlsTransportOptions options)
+    {
+        // Direct certificate object takes precedence
+        if (options.ServerCertificate is not null)
+        {
+            return options.ServerCertificate;
+        }
+
+        // Load from path
+        if (string.IsNullOrEmpty(options.ServerCertificatePath))
+        {
+            throw new InvalidOperationException("Server certificate is not configured");
+        }
+
+        return LoadCertificateFromPath(
+            options.ServerCertificatePath,
+            options.ServerCertificateKeyPath,
+            options.ServerCertificatePassword);
+    }
+
+    /// <summary>
+    /// Loads a client certificate from the options.
+    /// </summary>
+    /// <param name="options">The TLS transport options.</param>
+    /// <returns>The loaded certificate, or null if not configured.</returns>
+    public static X509Certificate2? LoadClientCertificate(TlsTransportOptions options)
+    {
+        // Direct certificate object takes precedence
+        if (options.ClientCertificate is not null)
+        {
+            return options.ClientCertificate;
+        }
+
+        // Load from path
+        if (string.IsNullOrEmpty(options.ClientCertificatePath))
+        {
+            return null;
+        }
+
+        return LoadCertificateFromPath(
+            options.ClientCertificatePath,
+            options.ClientCertificateKeyPath,
+            options.ClientCertificatePassword);
+    }
+
+    /// <summary>
+    /// Loads a certificate from a file path.
+    /// </summary>
+    /// <param name="certPath">The certificate path (PEM or PFX).</param>
+    /// <param name="keyPath">The private key path (optional, for PEM).</param>
+    /// <param name="password">The password (optional, for PFX).</param>
+    /// <returns>The loaded certificate.</returns>
+    public static X509Certificate2 LoadCertificateFromPath(
+        string certPath,
+        string? keyPath = null,
+        string? password = null)
+    {
+        var extension = Path.GetExtension(certPath).ToLowerInvariant();
+
+        return extension switch
+        {
+            ".pfx" or ".p12" => LoadPfxCertificate(certPath, password),
+            ".pem" or ".crt" or ".cer" => LoadPemCertificate(certPath, keyPath),
+            _ => throw new InvalidOperationException($"Unsupported certificate format: {extension}")
+        };
+    }
+
+    private static X509Certificate2 LoadPfxCertificate(string pfxPath, string? password)
+    {
+        return X509CertificateLoader.LoadPkcs12FromFile(
+            pfxPath,
+            password,
+            X509KeyStorageFlags.MachineKeySet | X509KeyStorageFlags.PersistKeySet);
+    }
+
+    private static X509Certificate2 LoadPemCertificate(string certPath, string? keyPath)
+    {
+        var certPem = File.ReadAllText(certPath);
+
+        if (string.IsNullOrEmpty(keyPath))
+        {
+            // Assume the key is in the same file
+            return X509Certificate2.CreateFromPem(certPem);
+        }
+
+        var keyPem = File.ReadAllText(keyPath);
+        return X509Certificate2.CreateFromPem(certPem, keyPem);
+    }
+}