🐛 (User and Group) Fixed issue #28 for Group. Improved fix for User

Group didn't return null values in requests. A line has been removed from User, because it was redondant (a general set of normalization_context in the call
to ApiResource)

Closes #28

Author: Teddy Roncin

src/Entity/Group.php

@@ -36,13 +36,15 @@
             'get' => [
                 'normalization_context' => [
                     'groups' => ['group:read:some'],
+                    'skip_null_values' => false,
                 ],
             ],
             'my_groups' => [
                 'method' => 'GET',
                 'path' => '/groups/me',
                 'normalization_context' => [
                     'groups' => ['group:read:some'],
+                    'skip_null_values' => false,
                 ],
             ],
             'post' => [
@@ -51,13 +53,15 @@
                 ],
                 'normalization_context' => [
                     'groups' => ['group:read:one'],
+                    'skip_null_values' => false,
                 ],
             ],
         ],
         itemOperations: [
             'get' => [
                 'normalization_context' => [
                     'groups' => ['group:read:one'],
+                    'skip_null_values' => false,
                 ],
             ],
             'delete' => [
@@ -70,6 +74,7 @@
                 ],
                 'normalization_context' => [
                     'groups' => ['group:read:one'],
+                    'skip_null_values' => false,
                 ],
                 'security' => "is_granted('patch', object)",
             ],

src/Entity/User.php

@@ -27,9 +27,6 @@
             'security' => "is_granted('ROLE_USER')",
             'pagination_items_per_page' => 10,
         ],
-        normalizationContext: [
-            'skip_null_values' => false,
-        ],
         collectionOperations: [
             'get' => [
                 'normalization_context' => [