Merge branch '2.2' into 2.3

Author: weaverryan

contributing/code/_api_tagging.rst.inc

@@ -0,0 +1,7 @@
+.. note::
+
+    If you think that one of our regular classes should have an ``@api`` tag,
+    put your request into a `new ticket on GitHub`_. We will then evaluate
+    whether we can add the tag or not.
+
+.. _new ticket on GitHub: https://github.com/symfony/symfony/issues/new