feat: implement Bundle and BundleItem models, migrations, and polymorphic relationships for cart and purchase items

app/Domains/Cart/Models/CartItem.php

@@ -10,7 +10,8 @@ use Illuminate\Database\Eloquent\Relations\BelongsTo;
 
 #[Fillable([
     'cart_id',
-    'producto_variante_id',
+    'buyable_id',
+    'buyable_type',
     'cantidad',
 ])]
 class CartItem extends Model
@@ -23,7 +24,8 @@ class CartItem extends Model
     {
         return [
             'cart_id' => 'integer',
-            'producto_variante_id' => 'integer',
+            'buyable_id' => 'integer',
+            'buyable_type' => 'string',
             'cantidad' => 'integer',
         ];
     }
@@ -37,10 +39,10 @@ class CartItem extends Model
     }
 
     /**
-     * @return BelongsTo<ProductVariant, $this>
+     * @return \Illuminate\Database\Eloquent\Relations\MorphTo
      */
-    public function variant(): BelongsTo
+    public function buyable()
     {
-        return $this->belongsTo(ProductVariant::class, 'producto_variante_id');
+        return $this->morphTo();
     }
 }