Adds release notes for v4.0.0 (#974)

* Adds release notes for v4.0.0

* Adds breaking change note

* Resolving comments

* Includes release notes for other FM packages

* Updates FM for v4 release

* Resolving comments

* Resolving comments

* Resolving comments

* Fixing issues

* Adding additional changes

* Added note to FM ASP.NET breaking changes

* Resolving comments

* Adjusted performance improvements

* Resolving comments

releaseNotes/Microsoft.Featuremanagement.AspNetCore.md

@@ -2,6 +2,29 @@
 
 [Source code][source_code] | [Package (NuGet)][package] | [Samples][samples] | [Product documentation][docs]
 
+## 4.0.0 - November 1, 2024
+
+### Enhancements
+
+* Adjusted the `.WithTargeting()` builder method to automatically add `HttpContextAccessor` if it's not already added.
+* Added `TargetingHttpContextMiddleware` which persists targeting context in the current activity. This is used when setting up [Telemetry](https://learn.microsoft.com/en-us/azure/azure-app-configuration/feature-management-dotnet-reference#telemetry).
+* Added support for variants in `FeatureTagHelper`. This allows MVC views to use the `<feature>` tag to conditionally render content based on whether a specific variant of a feature is assigned.
+
+    ``` HTML+Razor
+    <feature name="FeatureX" variant="Alpha">
+      <p>This can only be seen if variant 'Alpha' of 'FeatureX' is assigned.</p>
+    </feature>
+    ```
+
+    For more details on ASP.NET views and variants, see [here](https://learn.microsoft.com/en-us/azure/azure-app-configuration/feature-management-dotnet-reference#view).
+* Updated `Microsoft.FeatureManagement` reference to `4.0.0`. See the [release notes](./Microsoft.Featuremanagement.md) for more information on the changes.
+* Added support for .NET 9 as a target framework.
+
+### Breaking Change
+
+* The `FeatureTagHelper` constructor now requires an `IVariantFeatureManager` to support new variant functionality. While this class is typically not instantiated directly, any direct instantiation will need to be updated.
+* Removed .NET 7 as a target framework as .NET 7 is out of support.
+
 ## 4.0.0-preview5 - Oct 24, 2024
 
 * Updated `Microsoft.FeatureManagement` reference to `4.0.0-preview5`. See the [release notes](./Microsoft.Featuremanagement.md) for more information on the changes.

releaseNotes/Microsoft.Featuremanagement.Telemetry.ApplicationInsights.AspNetCore.md

@@ -2,6 +2,10 @@
 
 [Source code][source_code] | [Package (NuGet)][package] | [Samples][samples] | [Product documentation][docs]
 
+## Deprecated
+
+This package has been deprecated and it's functionality is now available as a part of the [Microsoft.FeatureManagement.ApplicationInsights](https://github.com/Azure/AppConfiguration/blob/main/releaseNotes/Microsoft.Featuremanagement.Telemetry.ApplicationInsights.md) package.
+
 ## 4.0.0-preview3 - April 10, 2024
 
 * Updated `Microsoft.FeatureManagement` reference to `4.0.0-preview3`. See the [release notes](./Microsoft.Featuremanagement.md) for more information on the changes.

releaseNotes/Microsoft.Featuremanagement.Telemetry.ApplicationInsights.md

@@ -2,6 +2,19 @@
 
 [Source code][source_code] | [Package (NuGet)][package] | [Samples][samples] | [Product documentation][docs]
 
+## 4.0.0 - November 1, 2024
+
+### Enhancements
+
+* Added support for Application Insights telemetry. To publish feature flag evaluation data and tag outgoing events with targeting information, register the Application Insights telemetry publisher as shown below.
+
+    ```csharp
+    builder.Services.AddFeatureManagement()
+        .AddApplicationInsightsTelemetry();
+    ```
+
+    For more details on Application Insights Publishing, see [here](https://learn.microsoft.com/en-us/azure/azure-app-configuration/feature-management-dotnet-reference#application-insights-telemetry-publisher)
+
 ## 4.0.0-preview5 - Oct 24, 2024
 
 * Updated `Microsoft.FeatureManagement` reference to `4.0.0-preview5`. See the [release notes](./Microsoft.Featuremanagement.md) for more information on the changes.

releaseNotes/Microsoft.Featuremanagement.md

@@ -2,6 +2,47 @@
 
 [Source code][source_code] | [Package (NuGet)][package] | [Samples][samples] | [Product documentation][docs]
 
+## 4.0.0 - November 1, 2024
+
+### Enhancements
+
+#### Variant Feature Flags
+
+A variant feature flag is an enhanced feature flag that supports multiple states or variations. While it can still be toggled on or off, it also allows for different configurations, ranging from simple primitives to complex JSON objects. Variant feature flags are particularly useful for feature rollouts, configuration rollouts, and feature experimentation (also known as A/B testing).
+
+The new `IVariantFeatureManager` has been introduced as the successor to the existing `IFeatureManager`. It retains all the functionalities of `IFeatureManager` while adding new `GetVariantAsync` methods and supporting `CancellationToken` for all methods.
+
+``` C#
+IVariantFeatureManager featureManager;
+...
+Variant variant = await featureManager.GetVariantAsync(MyFeatureFlags.HelpText, CancellationToken.None);
+model.Text = variant.Configuration.Value;
+```
+
+*Note: If reading variant flags from App Configuration, version `8.0.0` or above for the `Microsoft.Extensions.Configuration.AzureAppConfiguration` or `Microsoft.Azure.AppConfiguration.AspNetCore` package is required.*
+
+For more details on Variants, see [here](https://learn.microsoft.com/en-us/azure/azure-app-configuration/feature-management-dotnet-reference#variants).
+
+#### Variant Service Provider
+
+Variant feature flags can be used in conjunction with dependency injection to surface different implementations of a service for different users. This is accomplished by using the Variant Service Provider.
+
+For more details on Variant Service Provider, see [here](https://learn.microsoft.com/en-us/azure/azure-app-configuration/feature-management-dotnet-reference#variants-in-dependency-injection)
+
+#### Telemetry
+
+Telemetry provides observability into flag evaluations, offering insights into which users received specific flag results. This enables more powerful metric analysis, such as experimentation.
+
+For more details on Telemetry, see [here](https://learn.microsoft.com/en-us/azure/azure-app-configuration/feature-management-dotnet-reference#telemetry).
+
+#### Microsoft Feature Management Schema
+
+Added support for variant feature flags defined using [Microsoft Feature Management schema](https://github.com/microsoft/FeatureManagement/blob/c5fab16dbf1450dce0bbfe7c4207da735ff31916/Schema/FeatureManagement.v2.0.0.schema.json). Variants and telemetry can be declared using [Microsoft Feature Flag schema v2](https://github.com/microsoft/FeatureManagement/blob/c5fab16dbf1450dce0bbfe7c4207da735ff31916/Schema/FeatureFlag.v2.0.0.schema.json). Here is a [Sample](https://github.com/microsoft/FeatureManagement-Dotnet/blob/f47e188babea0a91488d2e6a0b2ab4c9405d0794/examples/VariantAndTelemetryDemo/appsettings.json#L12).
+
+#### Performance Optimizations
+
+* The performance of the feature flag state evaluation has been improved by up to 20%, with a memory reduction of up to 30% for .NET 8 applications compared to the version 3.5.0 release.
+
 ## 4.0.0-preview5 - Oct 24, 2024
 
 ### Enhancements