fix(configuration-database): resolve ConfigurationDatabase-002..007 — remove hardcoded sa creds, fail-fast no-arg DI, encrypt secret columns, resilient audit serialization

tests/ScadaLink.ConfigurationDatabase.Tests/ServiceCollectionExtensionsTests.cs

@@ -0,0 +1,57 @@
+using System.Reflection;
+using Microsoft.Extensions.DependencyInjection;
+using ScadaLink.Commons.Interfaces.Repositories;
+using ScadaLink.Commons.Interfaces.Services;
+using ScadaLink.ConfigurationDatabase;
+
+namespace ScadaLink.ConfigurationDatabase.Tests;
+
+public class ServiceCollectionExtensionsTests
+{
+    [Fact]
+    public void AddConfigurationDatabase_WithConnectionString_RegistersRepositoriesAndServices()
+    {
+        var services = new ServiceCollection();
+
+        services.AddConfigurationDatabase("DataSource=:memory:");
+
+        Assert.Contains(services, d => d.ServiceType == typeof(ITemplateEngineRepository));
+        Assert.Contains(services, d => d.ServiceType == typeof(IAuditService));
+        Assert.Contains(services, d => d.ServiceType == typeof(IInstanceLocator));
+    }
+
+    // The no-arg overload is [Obsolete(error: true)], so it cannot be referenced directly
+    // from source — that is the compile-time guard. Invoke it via reflection to verify the
+    // runtime defence-in-depth behaviour.
+    private static MethodInfo NoArgOverload =>
+        typeof(ServiceCollectionExtensions).GetMethod(
+            nameof(ServiceCollectionExtensions.AddConfigurationDatabase),
+            BindingFlags.Public | BindingFlags.Static,
+            binder: null,
+            types: new[] { typeof(IServiceCollection) },
+            modifiers: null)!;
+
+    [Fact]
+    public void AddConfigurationDatabase_NoArgOverload_FailsFastWithClearMessage()
+    {
+        // Regression guard for ConfigurationDatabase-003: the parameterless overload must not
+        // silently register nothing. Misuse must surface immediately at wire-up time with an
+        // actionable message — not later as an opaque DI resolution failure.
+        var services = new ServiceCollection();
+
+        var invocation = Assert.Throws<TargetInvocationException>(
+            () => NoArgOverload.Invoke(null, new object[] { services }));
+
+        var ex = Assert.IsType<InvalidOperationException>(invocation.InnerException);
+        Assert.Contains("connection string", ex.Message, StringComparison.OrdinalIgnoreCase);
+    }
+
+    [Fact]
+    public void AddConfigurationDatabase_NoArgOverload_IsMarkedObsoleteAsError()
+    {
+        // The no-op overload must be flagged so misuse is caught at compile time.
+        var obsolete = NoArgOverload.GetCustomAttribute<ObsoleteAttribute>();
+        Assert.NotNull(obsolete);
+        Assert.True(obsolete!.IsError);
+    }
+}