feature Sylius#10117 Upgrade guide from v1.3.X to v1.4.0 (Zales0123)

This PR was merged into the 1.4 branch.

Discussion
----------

| Q               | A
| --------------- | -----
| Branch?         | master
| Bug fix?        | no
| New feature?    | no
| BC breaks?      | no
| Deprecations?   | no
| Related tickets | 
| License         | MIT



Commits
-------

12ad01e Upgrade guide from `v1.3.X` to `v1.4.0`
49f9109 PR review fixes

UPGRADE-1.4.md

@@ -1,9 +1,51 @@
 # UPGRADE FROM `v1.3.X` TO `v1.4.0`
 
-* Deprecated not passing `Sylius\Component\Locale\Context\LocaleContextInterface` instance as the second argument 
-  to `Sylius\Bundle\LocaleBundle\Templating\Helper\LocaleHelper`'s constructor.
 
-* Due to switch to `doctrine/doctrine-migrations-bundle:^2.0`, some changes in migration files are required:
-    * `Doctrine\DBAL\Migrations\AbstractMigration` -> `Doctrine\Migrations\AbstractMigration`
-    * `Doctrine\DBAL\Migrations\SkipMigrationException` -> `Doctrine\Migrations\Exception\SkipMigration` (if used)
-    * `: void` return type added to both `up` and `down` methods
+The first step is upgrading Sylius with Composer
+
+- `composer require sylius/sylius:~1.4.0`
+
+### Doctrine migrations
+
+* Change base `AbstractMigration` namespace to `Doctrine\Migrations\AbstractMigration`
+* Add `: void` return types to both `up` and `down` functions
+* Copy [this](https://github.com/Sylius/Sylius-Standard/blob/1.4/src/Migrations/Version20190109095211.php) and [this](https://github.com/Sylius/Sylius-Standard/blob/1.4/src/Migrations/Version20190109160409.php) migration to your migrations folder or run `doctrine:migrations:diff` to generate new migration with changes from **Sylius**
+
+### Dotenv
+
+* `composer require symfony/dotenv:^4.2 --dev --no-update`
+* Follow [Symfony dotenv update guide](https://symfony.com/doc/current/configuration/dot-env-changes.html) to incorporate required changes in `.env` files structure. Optionally, you can take a look at [corresponding PR](https://github.com/Sylius/Sylius-Standard/pull/323) introducing these changes in **Sylius-Standard**
+
+At the apply migrations with `bin/console doctrine:migrations:migrate`.
+
+Don't forget to clear the cache (`bin/console cache:clear`) to be 100% everything is loaded properly.
+
+---
+
+### Behat
+
+If you're using Behat and want to be up-to-date with our configuration, introduce following changes (you can also take a look at [SymfonyExtension UPGRADE file](https://github.com/FriendsOfBehat/SymfonyExtension/blob/master/UPGRADE-2.0.md))
+for more details:
+
+* Update required extensions with `composer require friends-of-behat/symfony-extension:^2.0 friends-of-behat/page-object-extension:^0.3 --dev`
+* Remove extensions that are not needed with `composer remove friends-of-behat/context-service-extension friends-of-behat/cross-container-extension friends-of-behat/service-container-extension --dev`
+* Update your `behat.yml` - look at the diff [here](https://github.com/Sylius/Sylius-Standard/pull/322/files#diff-7bde54db60a6e933518d8b61b929edce)
+* Add `FriendsOfBehat\SymfonyExtension\Bundle\FriendsOfBehatSymfonyExtensionBundle::class => ['test' => true, 'test_cached' => true],` to your `bundles.php`
+* If you use our Travis CI configuration, follow [these changes](https://github.com/Sylius/Sylius-Standard/pull/322/files#diff-354f30a63fb0907d4ad57269548329e3) introduced in `.travis.yml` file
+* Create `config/services_test.yaml` file with the following code and add these your own Behat services as well:
+    ```yaml
+    imports:
+        - { resource: "../vendor/sylius/sylius/src/Sylius/Behat/Resources/config/services.xml" }
+    ```
+* If you use our Travis CI configuration, create also `config/services_test_cached.yaml` and import the `config/services_test.yaml` file:
+    ```yaml
+    imports:
+        - { resource: "services_test.yaml" }
+    ```
+* If you use our Travis CI configuration, follow [theses changes](https://github.com/Sylius/Sylius-Standard/pull/323/files#diff-354f30a63fb0907d4ad57269548329e3) introduced in `.travis.yml` file
+
+---
+
+### Deprecations
+
+- Not passing `Sylius\Component\Locale\Context\LocaleContextInterface` instance as the second argument to `Sylius\Bundle\LocaleBundle\Templating\Helper\LocaleHelper`'s constructor was deprecated