feat: carddav: support sync-token (#2230)

app/Models/User/SyncToken.php

@@ -0,0 +1,28 @@
+<?php
+
+namespace App\Models\User;
+
+use App\Models\ModelBinding as Model;
+
+class SyncToken extends Model
+{
+    protected $table = 'synctoken';
+
+    /**
+     * The attributes that aren't mass assignable.
+     *
+     * @var array
+     */
+    protected $guarded = ['id'];
+
+    /**
+     * The attributes that are mass assignable.
+     *
+     * @var array
+     */
+    protected $fillable = [
+        'account_id',
+        'user_id',
+        'timestamp',
+    ];
+}