Autoconfig environment `_FILE` variables

I just spent 1 hour googling and experimenting with my docker setup because nextcloud container would always use sqlite database no matter what I did.

Finally decided to look into the code and found https://github.com/nextcloud/docker/blob/f9ae675c1ac2aed735435e84dd1794eb28890103/.config/autoconfig.php#L23-L37

I think it's confusing to say that _FILE suffix is supported but not mentioning that if you want to use ONE variable from file (ie POSTGRES_PASSWORD), you have to use ALL variables from file...

Rather than documenting this behavior, I think it'd be more interesting to fix it and allow each variable independently such as

# pseudo-code

check_env($variable) {
 return getenv($variable) || getenv($variable + "_FILE")
}

...
} elseif (check_env('POSTGRES_DB_FILE') && check_env('POSTGRES_USER_FILE') && check_env('POSTGRES_PASSWORD_FILE') && check_env('POSTGRES_HOST')) {
...

Start in .config/autoconfig.php at lines 23-37 and inspect how the environment variables and their _FILE variants are checked. Reproduce the reported Docker setup with only POSTGRES_PASSWORD supplied from a file, then verify that each variable can independently use either form without forcing all database settings to come from files.