Merge branch 'rel-3.1' into dev

docs/en/Features.md

@@ -170,10 +170,14 @@ namespace FeaturesDemo
 
 > ABP automatically discovers this class and registers the features. No additional configuration required.
 
+> This class is generally created in the `Application.Contracts` project of your solution.
+
 * In the `Define` method, you first need to add a **feature group** for your application/module or get an existing group then add **features** to this group.
 * First feature, named `MyApp.PdfReporting`, is a `boolean` feature with `false` as the default value.
 * Second feature, named `MyApp.MaxProductCount`, is a numeric feature with `10` as the default value.
 
+Default value is used if there is no other value set for the current user/tenant.
+
 ### Other Feature Properties
 
 While these minimal definitions are enough to make the feature system working, you can specify the **optional properties** for the features;
@@ -339,15 +343,105 @@ See the [features](Features.md) document for the Angular UI.
 
 ## Feature Management
 
-TODO
+Feature management is normally done by an admin user using the feature management modal:
 
-## Advanced Topics
+![features-modal](images/features-modal.png)
+
+This modal is available on the related entities, like tenants in a multi-tenant application. To open it, navigate to the **Tenant Management** page (for a multi-tenant application), click to the **Actions** button left to the Tenant and select the **Features** action.
+
+If you need to manage features by code, inject the `IFeatureManager` service.
+
+**Example: Enable PDF reporting for a tenant**
+
+```csharp
+public class MyService : ITransientDependency
+{
+    private readonly IFeatureManager _featureManager;
+
+    public MyService(IFeatureManager featureManager)
+    {
+        _featureManager = featureManager;
+    }
 
-TODO
+    public async Task EnablePdfReporting(Guid tenantId)
+    {
+        await _featureManager.SetForTenantAsync(
+            tenantId,
+            "MyApp.PdfReporting",
+            true.ToString()
+        );
+    }
+}
+```
+
+`IFeatureManager` is defined by the Feature Management module. It comes pre-installed with the application startup template. See the [feature management module documentation](Modules/Feature-Management.md) for more information.
+
+## Advanced Topics
 
 ### Feature Value Providers
 
-TODO
+Feature system is extensible. Any class derived from `FeatureValueProvider` (or implements `IFeatureValueProvider`) can contribute to the feature system. A value provider is responsible to **obtain the current value** of a given feature.
+
+Feature value providers are **executed one by one**. If one of them return a non-null value, then this feature value is used and the other providers are not executed.
+
+There are three pre-defined value providers, executed by the given order:
+
+* `TenantFeatureValueProvider` tries to get if the feature value is explicitly set for the **current tenant**.
+* `EditionFeatureValueProvider` tries to get the feature value for the current edition. Edition Id is obtained from the current principal identity (`ICurrentPrincipalAccessor`) with the claim name `editionid` (a constant defined as`AbpClaimTypes.EditionId`). Editions are not implemented for the [tenant management](Modules/Tenant-Management.md) module. You can implement it yourself or consider to use the [SaaS module](https://commercial.abp.io/modules/Volo.Saas) of the ABP Commercial.
+* `DefaultValueFeatureValueProvider` gets the default value of the feature.
+
+You can write your own provider by inheriting the `FeatureValueProvider`.
+
+**Example: Enable all features for a user with "SystemAdmin" as a "User_Type" claim value**
+
+```csharp
+using System.Threading.Tasks;
+using Volo.Abp.Features;
+using Volo.Abp.Security.Claims;
+using Volo.Abp.Validation.StringValues;
+
+namespace FeaturesDemo
+{
+    public class SystemAdminFeatureValueProvider : FeatureValueProvider
+    {
+        public override string Name => "SA";
+
+        private readonly ICurrentPrincipalAccessor _currentPrincipalAccessor;
+
+        public SystemAdminFeatureValueProvider(
+            IFeatureStore featureStore,
+            ICurrentPrincipalAccessor currentPrincipalAccessor)
+            : base(featureStore)
+        {
+            _currentPrincipalAccessor = currentPrincipalAccessor;
+        }
+
+        public override Task<string> GetOrNullAsync(FeatureDefinition feature)
+        {
+            if (feature.ValueType is ToggleStringValueType &&
+                _currentPrincipalAccessor.Principal?.FindFirst("User_Type")?.Value == "SystemAdmin")
+            {
+                return Task.FromResult("true");
+            }
+
+            return null;
+        }
+    }
+}
+```
+
+If a provider returns `null`, then the next provider is executed.
+
+Once a provider is defined, it should be added to the `AbpFeatureOptions` as shown below:
+
+```csharp
+Configure<AbpFeatureOptions>(options =>
+{
+    options.ValueProviders.Add<SystemAdminFeatureValueProvider>();
+});
+```
+
+Use this code inside the `ConfigureServices` of your [module](Module-Development-Basics.md) class.
 
 ### Feature Store
 

docs/en/Modules/Feature-Management.md

@@ -1,3 +1,5 @@
 # Feature Management Module
 
+> This module implements the `IFeatureStore` to store and manage feature values in a database. See the [Features System document](../Features.md) to understand the features first.
+
 TODO

docs/en/Modules/Permission-Management.md

@@ -1,3 +1,5 @@
 # Permission Management Module
 
+This module implements the `IPermissionStore` to store and manage feature values in a database. See the [Authorization document](../Authorization.md) to understand the authorization and permission systems first.
+
 TODO