feat(core): DeferredServiceProvider für verzögerte IServiceProvider-Initialisierung hinzugefügt

DigitalData.Core.Abstractions/LazyServiceProvider.cs

@@ -0,0 +1,40 @@
+namespace DigitalData.Core.Abstractions;
+
+/// <summary>
+/// A deferred implementation of <see cref="IServiceProvider"/> that allows the <see cref="IServiceProvider"/> instance 
+/// to be provided at a later time via a factory callback.
+/// </summary>
+/// <remarks>
+/// This is particularly useful when service registration requires an <see cref="IServiceProvider"/> instance,
+/// but the service provider is not yet available at registration time. 
+/// By using <see cref="DeferredServiceProvider"/>, a service can safely resolve dependencies once
+/// the application's service provider has been built, ensuring a single consistent scope.
+/// </remarks>
+public class DeferredServiceProvider : IServiceProvider
+{
+    private Lazy<IServiceProvider>? _serviceProvider;
+
+    /// <summary>
+    /// Sets the factory that will be used to lazily initialize the <see cref="IServiceProvider"/> instance.
+    /// </summary>
+    public Func<IServiceProvider> Factory
+    {
+        set => _serviceProvider = new(value);
+    }
+
+    /// <summary>
+    /// Retrieves the requested service object from the deferred <see cref="IServiceProvider"/>.
+    /// </summary>
+    /// <param name="serviceType">The type of service object to retrieve.</param>
+    /// <returns>The requested service object, or <c>null</c> if the service is not available.</returns>
+    /// <exception cref="InvalidOperationException">
+    /// Thrown if the service provider factory has not been set before calling <see cref="GetService"/>.
+    /// </exception>
+    public object? GetService(Type serviceType)
+    {
+        if (_serviceProvider is null)
+            throw new InvalidOperationException("The service provider has not been initialized. Make sure 'Factory' is set before calling 'GetService'.");
+
+        return _serviceProvider.Value.GetService(serviceType);
+    }
+}