some bugs need to fix

[TiaNex-Com]

1. product has many productSkus

SQLSTATE[23000]: Integrity constraint violation: 1062 Duplicate entry '1-kg' for key 'mt_product_sku.mt_product_sku_index_product_id_attribute_name_61a108014425b'   
(1-kg ,"1" is product id and "kg" is attribute name)

string(194) "INSERT INTO `mt_product_sku` (`sequence`, `status`, `created_at`, `updated_at`, `ip_address`, `product_id`, `attribute_name`, `weight`, `price`, `quantity`) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?)"

the right action should be delete the same rows or ON DUPLICATE KEY UPDATE

2.Many To Many (product and category)
when add new category to product , error happend but remove

Transaction can't be finished. Some relations can't be resolved:
Create new `productCategory`
  - category.products:productCategory (Cycle\ORM\Relation\ShadowBelongsTo)

[roxblnfk]

1. You should check your indexes. I think that index mt_product_sku.mt_product_sku_index_product_id_attribute_name_61a108014425b shouldn't be unique or should contain additional field
   Oh i was wrong. Yes we need to fix this behavior. Add ODKU behavior or delete childs before adding them #350

2. Should be fixed here: https://github.com/cycle/orm/releases/tag/v2.1.1