As an administrator, I would like the ability to send a broadcast email to all users

Feature request

As an administrator, I would like the ability to send a broadcast email to all users. There should some kind 'email all users' feature that allow administrators to make announcement on the server.

Use cases

• Bitbucket Server will be offline for an extended or indefinite period of time and I need to notify users before it goes offline
  • e.g. My Bitbucket Server instance is moving to a new domain and I need to notify all users of the instance to update their bookmarks / git remotes / etc.
  • e.g. Bitbucket Server will be down for maintenance over the weekend and I need to notify all users so that there is a status page I can refer them to about the maintenance.
• I need to notify all users of Bitbucket Server, including the users that do not log in to the web interface frequently
  • e.g. We have switched to a new SSO provider and you will now need to use new login details to access Bitbucket Server.