Add .NET 10 validation package documentation

Co-authored-by: wadepickett <[email protected]>

Author: Copilot

aspnetcore/includes/validation-package-net10.md

@@ -0,0 +1,19 @@
+## Validation in .NET 10
+
+In .NET 10, the unified validation APIs have been moved to the `Microsoft.Extensions.Validation` NuGet package. This change makes the validation APIs available outside of ASP.NET Core HTTP scenarios.
+
+To use the `Microsoft.Extensions.Validation` APIs:
+
+* Add the following package reference:
+
+  ```xml
+  <PackageReference Include="Microsoft.Extensions.Validation" Version="10.0.0" />
+  ```
+
+  The functionality remains the same but now requires an explicit package reference.
+
+* Register validation services with dependency injection:
+
+```csharp
+builder.Services.AddValidation();
+```

aspnetcore/mvc/models/validation.md

@@ -16,6 +16,10 @@ This article explains how to validate user input in an ASP.NET Core MVC or Razor
 
 [View or download sample code](https://github.com/dotnet/AspNetCore.Docs/tree/main/aspnetcore/mvc/models/validation/samples) ([how to download](xref:index#how-to-download-a-sample)).
 
+:::moniker range=">= aspnetcore-10.0"
+[!INCLUDE[](~/includes/validation-package-net10.md)]
+:::moniker-end
+
 ## Model state
 
 Model state represents errors that come from two subsystems: model binding and model validation. Errors that originate from [model binding](xref:mvc/models/model-binding) are generally data conversion errors. For example, an "x" is entered in an integer field. Model validation occurs after model binding and reports errors where data doesn't conform to business rules. For example, a 0 is entered in a field that expects a rating between 1 and 5.

aspnetcore/tutorials/first-mvc-app/validation.md

@@ -27,6 +27,10 @@ One of the design tenets of MVC is [DRY](https://wikipedia.org/wiki/Don%27t_repe
 
 The validation support provided by MVC and Entity Framework Core is a good example of the DRY principle in action. You can declaratively specify validation rules in one place (in the model class) and the rules are enforced everywhere in the app.
 
+:::moniker range=">= aspnetcore-10.0"
+[!INCLUDE[](~/includes/validation-package-net10.md)]
+:::moniker-end
+
 ## Delete the previously edited data
 
 In the next step, validation rules are added that don't allow null values. 

aspnetcore/tutorials/razor-pages/validation.md

@@ -28,6 +28,10 @@ The validation support provided by Razor Pages and Entity Framework is a good ex
 * Validation rules are declaratively specified in one place, in the model class.
 * Rules are enforced everywhere in the app.
 
+:::moniker range=">= aspnetcore-10.0"
+[!INCLUDE[](~/includes/validation-package-net10.md)]
+:::moniker-end
+
 ## Add validation rules to the movie model
 
 The <xref:System.ComponentModel.DataAnnotations> namespace provides: