Update to v23.12

Update procedure for v23.12 version does not differ from the standard one, but docker-compose down command should be executed with --remove-orphans key due to container renaming.

However, v23.12 introduces several changes that require additional steps to be taken before running MITIGATOR. Such changes include:

end of support of the old data-plane.conf configuration file format existed before v20.08.
Renaming data-plane.conf file to dataplane.conf. Compatibility with the old name is maintained, but we recommend to update the file name.
Renaming data-plane container to dataplane.
Changes to pgfailover logic.
Transferring VPN settings to the base configuration file docker-compose.yml.

Therefore, when updating, make sure that:

data-plane.conf directory, if present, has been removed;
```
rmdir data-plane.conf
```

file data-plane.conf renamed to dataplane.conf;

mv data-plane.conf dataplane.conf || touch dataplane.conf

settings in dataplane.conf are set correctly;
in the new base configuration file docker-compose.yml and in all additional .yml specified in COMPOSE_FILE variable of .env file, the container name is changed to dataplane.

Get a list of files specified in COMPOSE_FILE:
```
cat .env | grep COMPOSE_FILE
```
COMPOSE_FILE variable in the .env file does not contain docker-compose.vpn.yml;

In docker-compose.failover.yml file, if there is one, BACKEND_PGFAILOVER_ADDRESS variable is set for backend service;

services:
  backend:
    environment:
      BACKEND_PGFAILOVER_ADDRESS: "${MITIGATOR_VPN_ADDRESS:-localhost}:50052"

In MITIGATOR Web interface, re-set the settings in the “HTTPS Challenge-Response Authentication” panel on the “Settings” page and in the HCA countermeasure, if they were previously set.