Merge branch '2.8' into 3.4

* 2.8:
  [Validation]  Added internal link

Author: javiereguiluz

validation.rst

@@ -472,7 +472,7 @@ options can be specified in this way.
 This is purely meant to make the configuration of the most common option of
 a constraint shorter and quicker.
 
-If you're ever unsure of how to specify an option, either check the API documentation
+If you're ever unsure of how to specify an option, either check :namespace:`Symfony\\Component\\Validator\\Constraints`
 for the constraint or play it safe by always passing in an array of options
 (the first method shown above).