minor #9286 Use 308 to ensure http method is preserved (greg0ire, javiereguiluz)

This PR was merged into the 2.7 branch.

Discussion
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Use 308 to ensure http method is preserved

307 and 308 were introduced exactly to solve this issue.

Commits
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e21cf2f Minor change
f8f6bda Added some minor explanation about 308 code
8549488 Use 308 to ensure http method is preserved

Author: javiereguiluz

routing/redirect_trailing_slash.rst

@@ -10,7 +10,7 @@ trailing slash to the same URL without a trailing slash
 
 Create a controller that will match any URL with a trailing slash, remove
 the trailing slash (keeping query parameters if any) and redirect to the
-new URL with a 301 response status code::
+new URL with a 308 (*HTTP Permanent Redirect*) response status code::
 
     // src/AppBundle/Controller/RedirectingController.php
     namespace AppBundle\Controller;
@@ -27,7 +27,9 @@ new URL with a 301 response status code::
 
             $url = str_replace($pathInfo, rtrim($pathInfo, ' /'), $requestUri);
 
-            return $this->redirect($url, 301);
+            // 308 (Permanent Redirect) is similar to 301 (Moved Permanently) except
+            // that it does not allow changing the request method (e.g. from POST to GET)
+            return $this->redirect($url, 308);
         }
     }
 
@@ -50,7 +52,7 @@ system, as explained below:
         {
             /**
              * @Route("/{url}", name="remove_trailing_slash",
-             *     requirements={"url" = ".*\/$"}, methods={"GET"})
+             *     requirements={"url" = ".*\/$"})
              */
             public function removeTrailingSlashAction(Request $request)
             {
@@ -65,7 +67,6 @@ system, as explained below:
             defaults: { _controller: AppBundle:Redirecting:removeTrailingSlash }
             requirements:
                 url: .*/$
-            methods: [GET]
 
     .. code-block:: xml
 
@@ -92,20 +93,10 @@ system, as explained below:
                 ),
                 array(
                     'url' => '.*/$',
-                ),
-                array(),
-                '',
-                array(),
-                array('GET')
+                )
             )
         );
 
-.. note::
-
-    Redirecting a POST request does not work well in old browsers. A 302
-    on a POST request would send a GET request after the redirection for legacy
-    reasons. For that reason, the route here only matches GET requests.
-
 .. caution::
 
     Make sure to include this route in your routing configuration at the