fix: make User::$id nullable

Author: kenjis

src/Entities/User.php

@@ -40,7 +40,7 @@ class User extends Entity
      * @var array<string, string>
      */
     protected $casts = [
-        'id'          => 'integer',
+        'id'          => '?integer',
         'active'      => 'boolean',
         'permissions' => 'array',
         'groups'      => 'array',

src/Models/UserModel.php

@@ -298,9 +298,7 @@ protected function saveEmailIdentity(array $data): array
         }
 
         // Insert
-        // If we use Entity Property Casting ['id' => 'integer'],
-        // `id` returns 0 when not set.
-        if ($this->tempUser->id === null || $this->tempUser->id === 0) {
+        if ($this->tempUser->id === null) {
             /** @var User $user */
             $user = $this->find($this->db->insertID());