Page editor tab for newsletters

[mgax]

The form to configure a newsletter campaign will be displayed in a new page edit tab.

Create a page mixin class named NewsletterPageMixin. It should define these fields:

• newsletter_recipients: foreign key to NewsletterRecipients. This field should persist outside of the revisions process (i.e. restoring a revision should not overwrite the value), see Spike: keep newsletter page fields out of revisions #10 for a way to do this.
• newsletter_subject: a string; may be empty, in which case the subject will be the page title.
• newsletter_campaign: a string; the ID of the campaign in the sending system (e.g. Mailchimp).

The mixin should provide a new page editor tab titled Newsletter. The tab should provide a chooser panel for recipients. More panels to be added later.

The prototype in models.py can serve as a reference.