feat: allow unauthenticated access to list of configs

This should simplify client code significantly according to platform#8849 (closed)

Closes #8800 (closed)

app/controllers/api/configs_controller.rb

 class Api::ConfigsController < ApiController
   include ControllerExtension::JsonFile
 
-  before_filter :require_login, :unless => :anonymous_access_allowed?
+  before_filter :require_login,
+    :unless => :anonymous_access_allowed?,
+    :except => :index
   before_filter :sanitize_id, only: :show
 
   def index