Debian package postupgrade script

[Tong Sun <suntong001@users.sourceforge.net>]

Hi,

I've been to
https://www.debian.org/doc/debian-policy/ch-maintainerscripts.html
but am still a bit lost on how to provide postupgrade script to my package.

I've made some breaking changes to my package,
https://github.com/suntong/dbab/commit/3ab123e5a90f2b37021a8a1b27dc6eaf2a9b87d6#diff-087e6c3b5855f52a443f266d08a555d1R77-R78
and would like to remove the old configure files in postupgrade step.

Would you be so kind as show me how it could be done please? Thanks!