Describe the bug
We have a system setup with pgcat and chose the APT repository as an installation method, just as described in the official docs. For the original installation, this works fine so far, but yields problems with upgrading the package: Each time we've upgraded the package, the service got stopped and the configuration file reset to the package maintainer's version. Effectively, this disabled pgcat and caused issues for all applications using pgcat (rendering a fatal exception).

To Reproduce
Since the APT repository only provides the most recent version of pgcat, the following steps "trick" APT into upgrading to the same version again, simulating an upgrade.

Steps to reproduce the behavior:

1. echo "deb [trusted=yes] https://apt.postgresml.org jammy main" | sudo tee -a /etc/apt/sources.list
2. sudo apt-get update
3. sudo apt-get install pgcat
4. Modify /etc/pgcat.toml to make some changes to the default configuration
5. sudo systemctl start pgcat
6. Trick APT into a fake, new version. Edit /var/lib/apt/lists/apt.postgresml.org_dists_jammy_main_binary-amd64_Packages and increase the version for pgcat temporarily:
   Before:

   Package: pgcat
   Version: 1.1.2-dev4
   # ...
   

   After:

   Package: pgcat
   Version: 1.1.2-dev5
   # ...
   

7. sudo apt-get upgrade pgcat
8. ⚡️ Check /etc/pgcat.toml: The previous modifications were lost, the file got replaced during the upgrade
9. ⚡️ Check the service status with sudo systemctl status pgcat: pgcat is no longer running.

Expected behavior
Upgrading pgcat through the official APT repository should 1) keep the current user configuration and 2) ensure that pgcat is in the same state as before (i.e., running).

Environment:

Distributor ID:	Ubuntu
Description:	Ubuntu 22.04.3 LTS
Release:	22.04
Codename:	jammy

pgcat 1.1.2-dev4