The new `--i18n-dir` directory allows the loading of an external
directory of i18n JSON files, milar to have `--static-dir`
works. New languages can be added and existing language files
can be customized this way.
This commit changes file loading behaviour so that invalid or
non-existent don't halt the execution of the app completely but
merely throw a warning and continue with the default (en) lang.
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.