Action sign-up without javascript

[richardolsson]

Implement links in the CampaignForm on www, to allow people to sign up without javascript enabled.

Link "sign-up" buttons to something like ?signup=<action_id>, and handle this on the server to sign them up and redirect them back to the form. Losing scroll position etc is an acceptable quality loss for the tiny minority for whom javascript does not work.

[richardolsson]

Moving this back to "In progress" because recent changes to another part of the activist portal requires this to change, and the changes should be made after a number of merges have been made to common.

[richardolsson]

Changed my mind. I'm leaving the working code for this in for now, even though the same functionality is implemented elsewhere as part of the "open campaigns" feature. See #222