Creation of MediaWiki Extension for Referring Users

The goal of this project is to create an extension for Mediawiki which enables registered users to refer other members through a referral link. For example, a user signs up and then has a personal referral link which he is able to give to others so that they can sign up to the site's wiki. There should be a count for each user and how many users he referred and also a list of all users and their referrals (preferably in a tree type list) This should be very easy to code. Side Note: Other projects are planned for this site, so possibility for more work on it will be available for the winner, if desired.