Documentation : how to add optional Broadcast message when secondary is promoted

Description

When the Geo node is a secondary, there are some indications the node is a secondary:

But after the node is promoted, this message is gone (because the node is writable now).

Is the absence of this bar enough to let users know they can now have write access on that node?

Proposal

Conclusion of the the discussion: Add to the documentation the admin can set a broadcast message to indicate the node is writable. It depends on their setup, i.e. whether they do a hostname change or not.

Links / references