Authz for membership confirmations

[adehnert]

I think we concluded that, now that we store the officers in the DB, requiring that a group admin submit the membership confirmation form is desirable.

I anticipate this will naturally combine with #27: both doing authz and requiring one submission per group per cycle naturally encourage picking the group before filling out the rest of the form.

[adehnert]

Fixed in:

commit 742e9c0b449fe1bb7f2d3a9d50a606ac0a0efd4e
Author: Alex Dehnert <adehnert@mit.edu>
Date:   Sun Nov 4 01:13:13 2012 -0500

    Finish support for group membership update cycles
    
    The revised workflow is that you visit a group selection page, and select a
    group to update. That checks authz (ASA-#169) and then loads any old update in
    the appropriate cycle (ASA-#27).

[adehnert]

Whoops, new hash: bda4d865e3f659470094cfdd2bebea96f326fe53.