feat: enforce tenant isolation and shared question bank

Tiku.Infrastructure/Tenancy/TenantExecutionScope.cs

@@ -0,0 +1,50 @@
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Logging;
+using Tiku.Application.Security;
+
+namespace Tiku.Infrastructure.Tenancy;
+
+public sealed class TenantExecutionScope(
+    IServiceScopeFactory scopeFactory,
+    ILogger<TenantExecutionScope> logger) : ITenantExecutionScope
+{
+    public Task ExecuteAsync(
+        Guid? targetTenantId,
+        string reason,
+        Func<IServiceProvider, CancellationToken, Task> operation,
+        CancellationToken cancellationToken = default)
+    {
+        return ExecuteAsync<object?>(
+            targetTenantId,
+            reason,
+            async (provider, token) =>
+            {
+                await operation(provider, token);
+                return null;
+            },
+            cancellationToken);
+    }
+
+    public async Task<TResult> ExecuteAsync<TResult>(
+        Guid? targetTenantId,
+        string reason,
+        Func<IServiceProvider, CancellationToken, Task<TResult>> operation,
+        CancellationToken cancellationToken = default)
+    {
+        ArgumentNullException.ThrowIfNull(operation);
+        if (string.IsNullOrWhiteSpace(reason))
+        {
+            throw new ArgumentException("A system scope requires an audit reason.", nameof(reason));
+        }
+
+        await using var scope = scopeFactory.CreateAsyncScope();
+        var initializer = scope.ServiceProvider.GetRequiredService<ITenantContextInitializer>();
+        initializer.InitializeSystem(targetTenantId, reason);
+        logger.LogWarning(
+            "Entering audited system tenant scope. TargetTenantId={TargetTenantId} Reason={Reason}",
+            targetTenantId,
+            reason);
+
+        return await operation(scope.ServiceProvider, cancellationToken);
+    }
+}