Required on view models (#15356)

* Added required on view models

* Updated OpenApi.json

* mark all fields required

* Force non-nullable as required.

* Missing import

* Update OpenApi.json

---------

Co-authored-by: Mads Rasmussen <madsr@hey.com>

src/Umbraco.Cms.Api.Management/ViewModels/User/ResendInviteUserRequestModel.cs

@@ -1,7 +1,10 @@
+using System.ComponentModel.DataAnnotations;
+
 namespace Umbraco.Cms.Api.Management.ViewModels.User;
 
 public class ResendInviteUserRequestModel
 {
+    [Required]
     public Guid UserId { get; set; } = Guid.Empty;
 
     public string? Message { get; set; }