UUF: Fix `AuthMessageSenderOptions` reg in auth tutorial

### Description

**Problem**
Users following the "Account confirmation and password recovery in ASP.NET Core" tutorial are experiencing an error: "`` throws error as undefined" when implementing email functionality.

**Root Cause**
The current documentation shows this code for registering the options:
```csharp
builder.Services.Configure(builder.Configuration);
```

This doesn't properly bind to any specific configuration section, causing the `AuthMessageSenderOptions` class to be undefined when injected into services.

**Proposed Solution**
Update the "Configure app to support email" section in the tutorial to properly register the `AuthMessageSenderOptions` class:

```csharp
// Add EmailSender as a transient service
builder.Services.AddTransient();
// Register the AuthMessageSenderOptions configuration instance
builder.Services.Configure(options =>
{
// Bind directly to the user secrets key
options.SendGridKey = builder.Configuration["SendGridKey"];
});
```

The key change here is in how the `AuthMessageSenderOptions` class gets registered.
Instead of using `builder.Services.Configure(builder.Configuration)`,
which doesn't properly bind to any specific configuration section, this update explicitly binds
the SendGridKey from the configuration to the options object.

This prevents the "`` throws error as undefined" error that can occur
when the options class isn't properly registered in the dependency injection container.

### Page URL

https://learn.microsoft.com/en-us/aspnet/core/security/authentication/accconfirm?view=aspnetcore-9.0&tabs=visual-studio

### Content source URL

https://github.com/dotnet/AspNetCore.Docs/blob/main/aspnetcore/security/authentication/accconfirm.md

### Document ID

98e7aacb-2a01-d581-9b03-bfef2893163e

### Platform Id

8efad4e0-06aa-bbe0-6133-4092aed18e42

### Article author

@wadepickett

### Metadata

* ID: fe1bea60-d173-f6d2-3559-b147699e295a
* PlatformId: 8efad4e0-06aa-bbe0-6133-4092aed18e42
* Service: **aspnet-core**
* Sub-service: **security**

[Related Issues](https://github.com/dotnet/AspNetCore.Docs/issues?q=is%3Aissue+is%3Aopen+98e7aacb-2a01-d581-9b03-bfef2893163e)