Merge branch '5.2' into 5.x

* 5.2:
  [Serializer] Clarifies 'csv_headers' option

Author: javiereguiluz

components/serializer.rst

@@ -897,7 +897,10 @@ Option                  Description                                           De
 ``csv_escape_char``     Sets the escape character (at most one character)
 ``csv_key_separator``   Sets the separator for array's keys during its        ``.``
                         flattening
-``csv_headers``         Sets the headers for the data                         ``[]``, inferred from input data's keys
+``csv_headers``         Sets the order of the header and data columns
+                        E.g.: ``serialize(['c' => 3,'a' => 1,'b' => 2],
+                        'csv', ['csv_headers' => ['a', 'b', 'c']]);``
+                        returns ``a,b,c\n1,2,3 ``                             ``[]``, inferred from input data's keys
 ``csv_escape_formulas`` Escapes fields containg formulas by prepending them   ``false``
                         with a ``\t`` character
 ``as_collection``       Always returns results as a collection, even if only