Merge pull request #291 from getsentry/document-plug-cookie-scrubber

document cookie scrubber

Author: mitchellhenke

docs/plug.rst

@@ -20,6 +20,10 @@ Optional settings
 
   The function to call before sending the headers of the request to Sentry.  It will default to ``Sentry.Plug.default_header_scrubber/1``, which will remove "Authorization" and "Authentication" headers.
 
+.. describe:: cookie_scrubber
+
+  The function to call before sending the cookies in the request to Sentry.  It will default to ``Sentry.Plug.default_cookie_scrubber/1``, which removes all cookie information.
+
 .. describe:: request_id_header
 
   If you're using Phoenix, Plug.RequestId, or another method to set a request ID response header, and would like to include that information with errors reported by Sentry.Plug, the `:request_id_header` option allows you to set which header key Sentry should check.  It will default to "x-request-id", which Plug.RequestId (and therefore Phoenix) also default to.