make a way to send server-wide messages from an admin panel

[iccanobif]

The same machinery for sending "system messages" to users could also be used for warnings such as the current "server-flood-detected" message, or warning that an user could be blocked because it was already removed from memory and we don't have its IP anymore.

[2sh]

What does the issue text have to do with an admin panel mentioned in the title?

[iccanobif]

just meant to say that, considering that right now we already have server-system-message events for sending messages from the server to the client without them being tied to a specific user id, server-wide messages/other warning messages could use the same event.