Confusing behavior when using --ah-cli to generate hashes for another environment

A lot of people seem to trip over the fact that in docker or systemd environments, the naive use of `--ah-cli` will produce incorrect hashes, due to the expectation that it will have access to the same generated `ah-salt`.

This can be solved by improving the documentation, but I am not certain what's the best solution here. So far I've been suggesting the following process:
1. add `show-ah-salt` to `[global]` section in the config
2. restart copyparty
3. check the log for a line that looks like `effective ah_salt is O4nO7p1ACFnuFk/EpcDdDM7H`
4. use the cli again to generate a password hash, using the same salt: `copyparty-sfx.py --ah-cli --ah-alg argon2 --ah-salt [ah_salt_you_saw_in_the_log]`

The alternative way could be to suggest setting `$XDG_CONFIG_HOME` in the call to `--ah-cli`, but the actual location seems to vary a lot depending on which systemd service implementation or docker is used. The file might also not be readable by the current user, making it not so straightforward.