Deprecate ActionDispatch::ParamsParser instance.

Related with 38d2bf5.

cc @tenderlove

Author: rafaelfranca

actionpack/CHANGELOG.md

@@ -1,3 +1,8 @@
+*   `ActionDispatch::ParamsParser` is deprecated and was removed from the middleware
+    stack. To configure the parameter parsers use `ActionDispatch::Request.parameter_parsers=`.
+
+    *tenderlove*
+
 *   When a `respond_to` collector with a block doesn't have a response, then
     a `:no_content` response should be rendered.  This brings the default
     rendering behavior introduced by https://github.com/rails/rails/issues/19036

actionpack/lib/action_dispatch/middleware/params_parser.rb

@@ -37,6 +37,7 @@ def original_exception
     # The +parsers+ argument can take Hash of parsers where key is identifying
     # content mime type, and value is a lambda that is going to process data.
     def self.new(app, parsers = {})
+      ActiveSupport::Deprecation.warn('ActionDispatch::ParamsParser is deprecated and you be removed in Rails 5.1. Configure the parameter parsing in ActionDispatch::Request.parameter_parsers.')
       parsers = parsers.transform_keys { |key| key.respond_to?(:symbol) ? key.symbol : key }
       ActionDispatch::Request.parameter_parsers = ActionDispatch::Request::DEFAULT_PARSERS.merge(parsers)
       app