Merge branch '4.4' into 5.4

* 4.4:
  [HttpClient] Fix seeking in not-yet-initialized requests
  [Serializer] Allow getting discriminated type by class name

Author: nicolas-grekas

Mapping/ClassDiscriminatorMapping.php

@@ -53,7 +53,7 @@ public function getClassForType(string $type): ?string
     public function getMappedObjectType($object): ?string
     {
         foreach ($this->typesMapping as $type => $typeClass) {
-            if (is_a($object, $typeClass)) {
+            if (is_a($object, $typeClass, true)) {
                 return $type;
             }
         }

Tests/Mapping/ClassDiscriminatorMappingTest.php

@@ -39,6 +39,7 @@ public function testMappedObjectType()
             'third' => AbstractDummyThirdChild::class,
         ]);
 
+        $this->assertEquals('first', $mapping->getMappedObjectType(AbstractDummyFirstChild::class));
         $this->assertEquals('first', $mapping->getMappedObjectType(new AbstractDummyFirstChild()));
         $this->assertNull($mapping->getMappedObjectType(new AbstractDummySecondChild()));
         $this->assertSame('third', $mapping->getMappedObjectType(new AbstractDummyThirdChild()));