Merge branch '5.2' into 5.x

* 5.2:
  Switched to non-null defaults in exception constructors
  Allow x-forwarded-prefix trusted header.

Author: derrabus

DependencyInjection/Configuration.php

@@ -98,7 +98,7 @@ public function getConfigTreeBuilder()
                     ->enumPrototype()
                         ->values([
                             'forwarded',
-                            'x-forwarded-for', 'x-forwarded-host', 'x-forwarded-proto', 'x-forwarded-port',
+                            'x-forwarded-for', 'x-forwarded-host', 'x-forwarded-proto', 'x-forwarded-port', 'x-forwarded-prefix',
                         ])
                     ->end()
                 ->end()

DependencyInjection/FrameworkExtension.php

@@ -2395,6 +2395,7 @@ private function resolveTrustedHeaders(array $headers): int
                 case 'x-forwarded-host': $trustedHeaders |= Request::HEADER_X_FORWARDED_HOST; break;
                 case 'x-forwarded-proto': $trustedHeaders |= Request::HEADER_X_FORWARDED_PROTO; break;
                 case 'x-forwarded-port': $trustedHeaders |= Request::HEADER_X_FORWARDED_PORT; break;
+                case 'x-forwarded-prefix': $trustedHeaders |= Request::HEADER_X_FORWARDED_PREFIX; break;
             }
         }