Hi, I don't think it is possible to set this up in Debconf or postinst. So, how about a note in "NEWS.Debian" and details in "README.Debian"?
Best Regards, Youhei -- Youhei SASAKI <uwab...@gfd-dennou.org> <uwab...@debian.or.jp> GPG fingerprint: 4096/RSA: 66A4 EA70 4FE2 4055 8D6A C2E6 9394 F354 891D 7E07