Ensure that boolean params in the API are parsed for truthiness (#6575)

Use Rails smart boolean cast to account for values such as "f",
"0", "false", etc. Previously, if a param was present in the request,
it would count as true.

app/controllers/api/base_controller.rb

@@ -51,6 +51,10 @@ class Api::BaseController < ApplicationController
     [params[:limit].to_i.abs, default_limit * 2].min
   end
 
+  def truthy_param?(key)
+    ActiveModel::Type::Boolean.new.cast(params[key])
+  end
+
   def current_resource_owner
     @current_user ||= User.find(doorkeeper_token.resource_owner_id) if doorkeeper_token
   end