Update 2. Demonstrate ability to process URLs in Magento.md

Author: simpleadm

2. Request Flow Processing/2. Demonstrate ability to process URLs in Magento.md

@@ -86,10 +86,12 @@ Module UrlRewrite:
 - \Magento\UrlRewrite\Model\UrlPersistInterface::replace
 
 Product:
-
-- event `catalog_product_save_after`
+- event `catalog_product_save_before` - generate URL key by product name (if url key wasn't provided)
+  * [ProductUrlKeyAutogeneratorObserver](https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/CatalogUrlRewrite/Observer/ProductUrlKeyAutogeneratorObserver.php)
+  * [\Magento\CatalogUrlRewrite\Model\ProductUrlPathGenerator::getUrlKey](https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/CatalogUrlRewrite/Model/ProductUrlPathGenerator.php#L125)
+- event `catalog_product_save_after` - generate and replace URL rewrites (if changed url_key, categories, websites or visibility)
   * [ProductProcessUrlRewriteSavingObserver](https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/CatalogUrlRewrite/Observer/ProductProcessUrlRewriteSavingObserver.php)
-  * \Magento\CatalogUrlRewrite\Model\ProductUrlRewriteGenerator::generate
+  * [\Magento\CatalogUrlRewrite\Model\ProductUrlRewriteGenerator::generate](https://github.com/magento/magento2/blob/2.2-develop/app/code/Magento/CatalogUrlRewrite/Model/ProductUrlRewriteGenerator.php#L128)
   * deleteByData, replace
 
 Category: