Merge branch '4.4' into 5.0

* 4.4:
  [PropertyAccess] fix tests
  [WebProfilerBundle] fix test
  remove assertions that can never be reached
  [PropertyAccess] Improve message of unitialized property in php 7.4
  [HttpFoundation] Fixed session migration with custom cookie lifetime
  [HttpKernel][FrameworkBundle] fix compat with Debug component
  [Serializer] Remove unused variable
  Allow URL-encoded special characters in basic auth part of URLs
  [Serializer] Fix unitialized properties (from PHP 7.4.2) when serializing context for the cache key
  [Validator] Add missing Ukrainian and Russian translations
  Track session usage when setting the token
  [4.4][MonologBridge] Fix $level type
  No need to reconnect the bags to the session
  Support for Content Security Policy style-src-elem and script-src-elem in WebProfiler
  [PropertyInfo][ReflectionExtractor] Check the array mutator prefixes last when the property is singular
  [Security][Http][SwitchUserListener] Ignore all non existent username protection errors
  Add installation and minimal example to README

Author: nicolas-grekas

README.md

@@ -3,10 +3,48 @@ Routing Component
 
 The Routing component maps an HTTP request to a set of configuration variables.
 
+Getting Started
+---------------
+
+```
+$ composer require symfony/routing
+```
+
+```php
+use App\Controller\BlogController;
+use Symfony\Component\Routing\Generator\UrlGenerator;
+use Symfony\Component\Routing\Matcher\UrlMatcher;
+use Symfony\Component\Routing\RequestContext;
+use Symfony\Component\Routing\Route;
+use Symfony\Component\Routing\RouteCollection;
+
+$route = new Route('/blog/{slug}', ['_controller' => BlogController::class]);
+$routes = new RouteCollection();
+$routes->add('blog_show', $route);
+
+$context = new RequestContext();
+
+// Routing can match routes with incoming requests
+$matcher = new UrlMatcher($routes, $context);
+$parameters = $matcher->match('/blog/lorem-ipsum');
+// $parameters = [
+//     '_controller' => 'App\Controller\BlogController',
+//     'slug' => 'lorem-ipsum',
+//     '_route' => 'blog_show'
+// ]
+
+// Routing can also generate URLs for a given route
+$generator = new UrlGenerator($routes, $context);
+$url = $generator->generate('blog_show', [
+    'slug' => 'my-blog-post',
+]);
+// $url = '/blog/my-blog-post'
+```
+
 Resources
 ---------
 
-  * [Documentation](https://symfony.com/doc/current/components/routing.html)
+  * [Documentation](https://symfony.com/doc/current/routing.html)
   * [Contributing](https://symfony.com/doc/current/contributing/index.html)
   * [Report issues](https://github.com/symfony/symfony/issues) and
     [send Pull Requests](https://github.com/symfony/symfony/pulls)