Merge pull request #8509 from abpframework/enisn/rel-4.3/docs/global-features

Docs - Add GlobalFeatures Documentation

docs/en/Global-Features.md

@@ -1,3 +1,117 @@
 # Global Features
+The purpose of the Global Feature System is to **add a module to your application but disable the features you don't want to use** (or enable only the ones you need). Notice that the features are not determined on runtime, you must select the features **on development time**. Because it will not create database tables, APIs and other stuff for unused features, which is not possible to change then on the runtime.
 
-TODO (see [#5061](https://github.com/abpframework/abp/issues/5061) until this is documented).
+## Installation
+> This package is already installed by default with the startup template. So, most of the time, you don't need to install it manually.
+
+### Using the ABP CLI
+
+Open a command line window in the folder of the project (.csproj file) and type the following command:
+
+```bash
+abp add-package Volo.Abp.GlobalFeatures
+```
+
+## Implementation
+
+Global Feature system aims module based feature management . A module has to have own Global Features itself.
+
+### Define a Global Feature
+
+A feature class is something like that:
+
+```csharp
+[GlobalFeatureName(Name)]
+public class PaymentFeature : GlobalFeature
+{
+    public const string Name = "Shopping.Payment";
+
+    public PaymentFeature(GlobalModuleFeatures module) : base(module)
+    {
+    }
+}
+```
+
+### Define Global Module Features
+
+All features of a module have to be defined in a Global Module Features class.
+
+```csharp
+public class GlobalShoppingFeatures : GlobalModuleFeatures
+{
+    public const string ModuleName = "Shopping";
+
+    public GlobalShoppingFeatures(GlobalFeatureManager featureManager) : base(featureManager)
+    {
+        AddFeature(new PaymentFeature(this));
+        // And more features...
+    }
+}
+```
+
+## Usage
+
+### Enable/Disable Features
+
+Global features are managed  by modules. Module Features have to be added to Modules of GlobalFeatureManager.
+
+```csharp
+// GerOrAdd might be useful to be sure module features are added.
+var shoppingGlobalFeatures = GlobalFeatureManager.Instance.Modules
+    .GetOrAdd(
+        GlobalShoppingFeatures.ModuleName, 
+        ()=> new GlobalShoppingFeatures(GlobalFeatureManager.Instance));
+
+// Able to Enable/Disable with generic type parameter.
+shoppingGlobalFeatures.Enable<PaymentFeature>();
+shoppingGlobalFeatures.Disable<PaymentFeature>();
+
+// Also able to Enable/Disable with string feature name.
+shoppingGlobalFeatures.Enable(PaymentFeature.Name);
+shoppingGlobalFeatures.Disable("Shopping.Payment");
+```
+
+### Check if a feature is enabled
+
+```csharp
+GlobalFeatureManager.Instance.IsEnabled<PaymentFeature>()
+GlobalFeatureManager.Instance.IsEnabled("Shopping.Payment")
+```
+
+Both methods return `bool`.
+
+```csharp
+if (GlobalFeatureManager.Instance.IsEnabled<PaymentFeature>())
+{
+    // Some strong payment codes here...
+}
+```
+
+Beside the manual check, there is `[RequiresGlobalFeature]` attribute to check it declaratively for a controller or page. ABP returns 404 if the related feature was disabled.
+
+```csharp
+[RequiresGlobalFeature(typeof(CommentsFeature))]
+public class PaymentController : AbpController
+{
+  // ...
+}
+```
+
+## When to configure Global Features?
+Global Features have to be configured before application startup. So best place to configuring it is `PreConfigureServices` with **OneTimeRunner** to make sure it runs one time.
+
+```csharp
+private static readonly OneTimeRunner OneTimeRunner = new OneTimeRunner();
+public override void PreConfigureServices(ServiceConfigurationContext context)
+{
+  OneTimeRunner.Run(() =>
+  {
+  	GlobalFeatureManager.Instance.Modules.Foo().EnableAll();
+  });
+}
+```
+
+## Features vs Global Features
+[Features](Features.md) & [Global Features](Global-Features.md) are totally different systems.
+
+Features are used to switch on/off application feature for each tenant. So Features, only hides disabled ones, but with Global Features, disabled features pretends like never existed in application.