Move config-files from /etc into /etc/foobar during package upgrade

[Daniel Leidert <daniel.leidert.spam@gmx.net>]

Hello,

I'm currently preparing an update for a package. Until now, the
configuration file(s) was/were located in /etc. Now there are changes,
which make it more useful to have the configuration files
inside /etc/foobar. The configuration files look like foobar.conf*.

Are there special things I need to care of? Does anyone know a package,
where the configuration files moved? I already added a NEWS file. But
not every user installed apt-listchanges, so I should also inform him
during update. Is it enough, do this on command-line or should I better
use a debconf-dialog? Is it enough to only inform the user or should I
better ask him [1], if his configuration files should be moved? What
would you do?

[1] If the files are not moved, the package breaks. Alternatively I
could (re)add /etc as search-path for the config-files, but moving the
files is really recommended. Would you add this backwards compatibility
"option"?

PS: I know, these are very generic information.

Regards, Daniel