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.
# File actionpack/lib/action_dispatch/middleware/params_parser.rb, line 39
def self.new(app, parsers = {})
ActiveSupport::Deprecation.warn('ActionDispatch::ParamsParser is deprecated and will 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
end