Add more information on how install and configure the FOSUserBundle (#256)

Author: piotaixr

core/fosuser-bundle.md

@@ -1,7 +1,35 @@
 # FOSUser Bundle Integration
 
-API Platform Core is shipped with a bridge for [FOSUserBundle](https://github.com/FriendsOfSymfony/FOSUserBundle). If the
-FOSUser bundle is enabled, this bridge will use its `UserManager` to create, update and delete user resources.
+API Platform Core is shipped with a bridge for [FOSUserBundle](https://github.com/FriendsOfSymfony/FOSUserBundle). If
+the FOSUser bundle is enabled, this bridge will use its `UserManager` to create, update and delete user resources.
+
+## Installing the Bundle
+
+The installation procedure of the FOSUserBundle is described [in the main Symfony docs](https://symfony.com/doc/master/bundles/FOSUserBundle/index.html)
+
+You can:
+- Skip the [step 3 (Create your User class)](https://symfony.com/doc/master/bundles/FOSUserBundle/index.html#step-3-create-your-user-class)
+and use the class provided in the next paragraph to set up serialization groups the correct way
+- Skip the [step 4 (Configure your application's security.yml)](https://symfony.com/doc/master/bundles/FOSUserBundle/index.html#step-4-configure-your-application-s-security-yml)
+if you are planning to [use a JWT-based authentication using `LexikJWTAuthenticationBundle`](jwt.md)
+
+If you are using the API Platform Standard Edition, you will need to enable the form services in the symfony framework
+configuration options:
+
+```yaml
+# app/config/config.yml
+framework:
+    form: { enabled: true }
+```
+
+## Enabling the Bridge
+
+To enable the provided bridge with FOSUserBundle, you need to add the following configuration to api-platform:
+```yaml
+# app/config/config.yml
+api_platform:
+    enable_fos_user: true
+```
 
 ## Creating a `User` Entity with Serialization Groups
 

index.md

@@ -86,7 +86,9 @@
         3.  [Configure it](core/operation-path-naming.md#configure-it)
 19. [Accept `application/x-www-form-urlencoded` Form Data](core/form-data.md)
 20. [FOSUserBundle Integration](core/fosuser-bundle.md)
-    1.  [Creating a `User` Entity with Serialization Groups](core/fosuser-bundle.md#creating-a-user-entity-with-serialization-groups)
+    1.  [Installing the Bundle](core/fosuser-bundle.md#installing-the-bundle)
+    2.  [Enabling the Bridge](core/fosuser-bundle.md#enabling-the-bridge)
+    3.  [Creating a `User` Entity with Serialization Groups](core/fosuser-bundle.md#creating-a-user-entity-with-serialization-groups)
 21. [Adding a JWT authentication using LexikJWTAuthenticationBundle](core/jwt.md)
 22. [NelmioApiDocBundle integration](core/nelmio-api-doc.md)
 23. [AngularJS Integration](core/angularjs-integration.md)