In the server settings.
Is there any documentation about this option ?
I don't think so, but there's not much to document. It's just a single text field.
It is possible to send announcement to specific users in order to annonce something like an event etc.. ?
No, the announcement shows up globally on the login screen. If you want to send something to specific users, why you can't just use email or SMS?
Scheduled announcement would be a great option to notify users
Hello,
Please where can we configure announcements for users ?