Merge branch '7.0' into 7.1

* 7.0:
  [HttpClient][Mailer] Revert "Let curl handle transfer encoding", use HTTP/1.1 for Mailgun
  Reviewed Catalan missing translations
  [AssetMapper] Upgrade importmap polyfill
  Fix typo: synchronous -> synchronously
  [Serializer] Check if exception message in test is correct
  Ibexa is sponsoring Symfony 5.4, thanks to them! \o/
  [VarDumper] Fix `FFICaster` test to be platform-adaptable
  [String] Add `alias` case to `EnglishInflector`
  [FrameworkBundle] Throw runtime exception when trying to use asset-mapper while http-client is disabled
  [SecurityBundle] Remove unused memory users’ `name` attribute from the XSD
  [VarExporter] generate __doUnserialize() method in ProxyHelper::generateLazyProxy()
  Double check if pcntl function exists
  Add additional headers in Scaleway bridge
  [VarDumper] Fix FFI caster test
  [DependencyInjection] Add test coverage for `AutowireCallable::buildDefinition()`

Author: nicolas-grekas

CurlHttpClient.php

@@ -250,8 +250,9 @@ public function request(string $method, string $url, array $options = []): Respo
 
             if (isset($options['normalized_headers']['content-length'][0])) {
                 $curlopts[\CURLOPT_INFILESIZE] = (int) substr($options['normalized_headers']['content-length'][0], \strlen('Content-Length: '));
-            } elseif (!isset($options['normalized_headers']['transfer-encoding'])) {
-                $curlopts[\CURLOPT_INFILESIZE] = -1;
+            }
+            if (!isset($options['normalized_headers']['transfer-encoding'])) {
+                $curlopts[\CURLOPT_HTTPHEADER][] = 'Transfer-Encoding:'.(isset($curlopts[\CURLOPT_INFILESIZE]) ? '' : ' chunked');
             }
 
             if ('POST' !== $method) {