Change membership button functionality

Open

Due	2020/11/05
Actionees	Bryan Hilderbrand,Mark Hershberger
Labels	Label:mwstake site

Details:
Should be group dependant:

• For a user (non-member) it should read "Become a Member" and take the user to Special:Subscribe
• For a member (non-corporate) it should read "Change Membership" and take the user to a page with choices:
  1. One for cancelling their membership (Special:Subscribe which is the same base as above but different functionality)
  2. Another to become a corporate member (SubscribeCorporate)