Allow Upper Case property names in ObjectNormalizer

| Q                | A
| ---------------- | -----
| Bug report?      | yes
| Feature request? | no
| BC Break report? | yes
| RFC?             | no
| Symfony version  | 2.8.19

Same problem that has been fixed here symfony/symfony#22265
and here api-platform/core#1037

ObjectNormalizer returns $id instead of $Id. It is bad naming convention, but is possible

```php
class Entity {
    protected $Id;

    public function getId()
    {
        return $this->Id;
    }
}
```

Author: insekticid

Normalizer/ObjectNormalizer.php

@@ -208,10 +208,22 @@ private function extractAttributes($object)
 
             if (0 === strpos($name, 'get') || 0 === strpos($name, 'has')) {
                 // getters and hassers
-                $attributes[lcfirst(substr($name, 3))] = true;
+                $propertyName = substr($name, 3);
+
+                if (!$reflClass->hasProperty($propertyName)) {
+                    $propertyName = lcfirst($propertyName);
+                }
+
+                $attributes[$propertyName] = true;
             } elseif (strpos($name, 'is') === 0) {
                 // issers
-                $attributes[lcfirst(substr($name, 2))] = true;
+                $propertyName = substr($name, 2);
+
+                if (!$reflClass->hasProperty($propertyName)) {
+                    $propertyName = lcfirst($propertyName);
+                }
+
+                $attributes[$propertyName] = true;
             }
         }
 

Tests/Normalizer/ObjectNormalizerTest.php

@@ -488,6 +488,11 @@ public function testNormalizeStatic()
         $this->assertEquals(array('foo' => 'K'), $this->normalizer->normalize(new ObjectWithStaticPropertiesAndMethods()));
     }
 
+    public function testNormalizeUpperCaseAttributes()
+    {
+        $this->assertEquals(array('Foo' => 'Foo', 'Bar' => 'BarBar'), $this->normalizer->normalize(new ObjectWithUpperCaseAttributeNames()));
+    }
+
     public function testNormalizeNotSerializableContext()
     {
         $objectDummy = new ObjectDummy();
@@ -662,3 +667,14 @@ public static function getBaz()
         return 'L';
     }
 }
+
+class ObjectWithUpperCaseAttributeNames
+{
+    private $Foo = 'Foo';
+    public $Bar = 'BarBar';
+
+    public function getFoo()
+    {
+        return $this->Foo;
+    }
+}