Save campaign content (as draft)

[mgax]

The editor should have the option to create a campaign in Mailchimp, and update its configuration and content, without sending test emails, or scheduling/sending the campaign itself.

The "Newsletter" editor tab should have a button, "Save campaign", that will trigger an API call to the server, which will call the campaign backend's save_campaign method.

The page should check whether there are any unsaved changes and prompt the editor to save their changes, otherwise the CMS backend will be sending stale data to Mailchimp.

Add a link in the "Newsletter" tab to the campaign page in the Mailchimp web app.

• For draft campaigns, the URL is https://{server}.admin.mailchimp.com/campaigns/edit?id={campaign_web_id}.
• For sent campaigns, the URL is https://{server}.admin.mailchimp.com/campaigns/show?id={campaign_web_id}.