The earlier approach of loading `/api/config.js` as a script on
initial page load with the necessary variables to init the UI is
ditched. Instead, it's now `/api/config` and `/api/settings` like
all other API calls. On load of the frontend, these two resources
are fetched and the frontend is initialised.
In addition to generating HTML forms for selected public lists,
the form page now shows a URL (/subscription/form) that can be
publicly shared to solicit subscriptions. The page lists all
public lists in the database. This page can be disabled on the
Settings UI.
This is a major feature that builds upon the `Messenger` interface
that has been in listmonk since its inception (with SMTP as the only
messenger). This commit introduces a new Messenger implementation, an
HTTP "postback", that can post campaign messages as a standard JSON
payload to arbitrary HTTP servers. These servers can in turn push them
to FCM, SMS, or any or any such upstream, enabling listmonk to be a
generic campaign messenger for any type of communication, not just
e-mails.
Postback HTTP endpoints can be defined in settings and they can be
selected on campaigns.
- A check for new versions on the GitHub releases pages happens
once every 24 hours. When a new version is available, a notice
is displayed on the admin UI.
