minor #10312 [Serializer] Allow to pass a single value for the groups opt (dunglas, javiereguiluz)

This PR was merged into the master branch.

Discussion
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[Serializer] Allow to pass a single value for the groups opt

symfony/symfony#27503

Commits
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ae558f4 Added the missing versionadded directive
e4eae25 Replaced a "note" by a "tip"
5e0a91e [Serializer] Allow to pass a single value for the groups opt

Author: javiereguiluz

components/serializer.rst

@@ -337,7 +337,7 @@ You are now able to serialize only attributes in the groups you want::
     $normalizer = new ObjectNormalizer($classMetadataFactory);
     $serializer = new Serializer(array($normalizer));
 
-    $data = $serializer->normalize($obj, null, array('groups' => array('group1')));
+    $data = $serializer->normalize($obj, null, array('groups' => 'group1'));
     // $data = array('foo' => 'foo');
 
     $obj2 = $serializer->denormalize(

serializer.rst

@@ -130,9 +130,16 @@ to your class and choose which groups to use when serializing::
 
     $json = $serializer->serialize(
         $someObject,
-        'json', array('groups' => array('group1'))
+        'json', array('groups' => 'group1')
     );
 
+.. tip::
+
+    The value of the ``groups`` key can be a single string, or an array of strings.
+    
+    .. versionadded:: 4.2
+        The option to pass a single string to ``groups`` was introduced in Symfony 4.2.
+
 In addition to the ``@Groups`` annotation, the Serializer component also
 supports YAML or XML files. These files are automatically loaded when being
 stored in one of the following locations: