Merge branch '5.1' into master

* 5.1:
  fix merge
  [Cache] fix previous PR
  add mising sr (latn & cyrl) translations
  [Cache] fix ProxyAdapter not persisting items with infinite expiration
  [HttpClient] fail properly when the server replies with HTTP/0.9
  Fix CS
  [Cache] Limit cache version character range
  [Mailer] Fixed Mailgun API bridge JsonException when API response is not applicaton/json
  [String] improve fix
  fix tests
  [DI] dump OS-indepent paths in the compiled container
  [DI] dump OS-indepent paths in the preload file
  Run postgres setup trigger in transaction
  allow consumers to mock all methods

Author: xabbuh

Tests/Command/CacheClearCommand/CacheClearCommandTest.php

@@ -84,6 +84,6 @@ public function testCacheIsFreshAfterCacheClearedWithWarmup()
         $containerFile = str_replace('tes_'.\DIRECTORY_SEPARATOR, 'test'.\DIRECTORY_SEPARATOR, $containerRef->getFileName());
         $this->assertMatchesRegularExpression(sprintf('/\'kernel.container_class\'\s*=>\s*\'%s\'/', $containerClass), file_get_contents($containerFile), 'kernel.container_class is properly set on the dumped container');
 
-        $this->assertFileEquals(__DIR__.'/Fixture/preload.php.expected', __DIR__.'/Fixture/preload.php');
+        $this->assertFileEquals(__DIR__.'/Fixture/preload.php.expected', __DIR__.'/Fixture/.preload.php');
     }
 }