Implemented basic user auth, register, login, details and avatar stuff from helio

Moonlight/App/Models/Forms/UpdateUserForm.cs

@@ -0,0 +1,16 @@
+using System.ComponentModel.DataAnnotations;
+
+namespace Moonlight.App.Models.Forms;
+
+public class UpdateUserForm
+{
+    [Required(ErrorMessage = "You need to enter a username")]
+    [MinLength(7, ErrorMessage = "The username is too short")]
+    [MaxLength(20, ErrorMessage = "The username cannot be longer than 20 characters")]
+    [RegularExpression("^[a-z][a-z0-9]*$", ErrorMessage = "Usernames can only contain lowercase characters and numbers")]
+    public string Username { get; set; } = "";
+    
+    [Required(ErrorMessage = "You need to enter a email address")]
+    [EmailAddress(ErrorMessage = "You need to enter a valid email address")]
+    public string Email { get; set; } = "";
+}