[FA-55] User Service backend initial setup

FictionArchive.Service.UserService/Models/DTOs/UserDto.cs

@@ -7,9 +7,10 @@ public class UserDto
     public Guid Id { get; init; }
     public Instant CreatedTime { get; init; }
     public Instant LastUpdatedTime { get; init; }
+
     public required string Username { get; init; }
     public required string Email { get; init; }
-    // OAuthProviderId intentionally omitted for security
     public bool Disabled { get; init; }
-    public UserDto? Inviter { get; init; }
+    public int AvailableInvites { get; init; }
+    public Guid? InviterId { get; init; }
 }