Custom validation class attributes

By simply using the edit form, input components, and DataAnnotationValidator, the framework will automatically add classes to the components when it's valid and when it's not valid.

By default, these classes are .valid and .invalid. In .NET 5, we are given a way to customize these class names ourselves.

When using Bootstrap, the default class names are .is-valid and .is-invalid and the class names must also have .form-control to get the right styles.

The component we are building next will help us to get the right Bootstrap styling on all of our form components.

We will create our own FieldCssClassProvider to customize what classes Blazor will use:

1. In the MyBlogServerSide project, right-click in the Components folder and select Add class, and name the class BootstrapFieldCssClassProvider.
2. Open the new class and add the following code:

   using Microsoft.AspNetCore.Components.Forms;
   using System.Linq;
   namespace MyBlogServerSide...