Feature request: notify users by email about new broadcasted messages

Problem to solve

Having a standalone gitlab instance with multiple geo separated users and let's suppose we need to schedule maintainance hours. At this moment GitLab has implemented feature called "Broadcast message", but these messages only shown if a developer is using gitlab actively. However this might not be always true - some developers only need gitlab to retrieve clone url. After that, they perform push/pull on their repositories by using only git cli. So they might be not informed about scheduled maintenance.

Proposal

Provide a way to inform users about all broadcasted messages by sending emails to them.