I wonder if anything has changed, or if they might be a workaround? Basically I would like to set a server-level configuration that says something like "Sorry, our system is under construction." any time a user encounters an error.
I know I can sanitize errors at the level of individual shiny apps, but would like a server-level option that allows a custom message if this is available.
Unfortunately this is still not a supported option, but we'll gladly add your vote! You can create system wide message banners for both logged out and logged in users.
If you're sending out links and you want them to be stable, be sure to use Vanity URLs. That way as you work on updating applications or reports you can publish them separately, and then roll over the vanity URL. This gives you an easy way to share stable links even if the underlying content is changing.
That's a shame. It looks like the underlying software is already using a variable to decide what message is being displayed. It seems like the lift to make this configurable should be relatively light.
If there is a way to vote for this feature on a backlog somewhere, I'd definitely add my vote!