add shipping rules

app/Models/Shop/Invoice.php

@@ -4,7 +4,6 @@ namespace App\Models\Shop;
 
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\SoftDeletes;
-
 use Venturecraft\Revisionable\RevisionableTrait;
 use Znck\Eloquent\Traits\BelongsToThrough;
 
@@ -13,8 +12,11 @@ class Invoice extends Model
     use BelongsToThrough, RevisionableTrait, SoftDeletes;
 
     protected $guarded = ['id'];
+
     protected $table = 'shop_invoices';
+
     protected $revisionCreationsEnabled = false;
+
     protected $keepRevisionOf = ['status', 'total_taxed', 'shipping', 'total_shipped'];
 
     public function payments()