Merge branch '5.1'

* 5.1:
  Add SameSite=None documentation

Author: javiereguiluz

reference/configuration/framework.rst

@@ -1317,6 +1317,10 @@ The possible values for this option are:
 
 * ``null``, use it to disable this protection. Same behavior as in older Symfony
   versions.
+* ``'none'`` (or the ``Cookie::SAMESITE_NONE`` constant), use it to allow 
+  sending of cookies when the HTTP request originated from a different domain 
+  (previously this was the default behavior of null, but in newer browsers ``'lax'``
+  would be applied when the header has not been set)
 * ``'strict'`` (or the ``Cookie::SAMESITE_STRICT`` constant), use it to never
   send any cookie when the HTTP request is not originated from the same domain.
 * ``'lax'`` (or the ``Cookie::SAMESITE_LAX`` constant), use it to allow sending