We need the option to display system messages in Tryton.
The purpose is to inform user on activities, problems or upcoming events with a pop-up message.
As example, an important message for the Demo-DB could be
'Dont change the language of the admin-account!' or 'The Demo-Database is reset each night at 0200 CET'
The system message should be displayed exactly 1 time to the user:
- at time of login, if a message is available
- immediately, in case the message is created while the user is already logged-in.
It should be possible to enter more than one system message. All available messages should be displayed in the same pop-up, together with the user (name|ID) who created the message.
There should be a possibility to set an expiry date and time for each message
System message maintenance should be part of the admin menu, and only with admin authorisations