custom date format for logging with datetime in filename

[xsolinsx]

Description

Building on #3210 and #3330, I would like to specify a custom format for datetime in the configuration

I am asking this because the american format is not ideal to me, I prefer having something that follows a logical order of year-month-day hour:minute:second

Use Case

having a specifiable format inside the configuration would allow authelia to write to the same log file if the format allows it
i.e.
let's say that the option is called "datetime_format" and is set as "year-month-day" (sorry, I don't know the Go syntax for datetimes)
in this case, if I restart authelia multiple times during the day to debug something, I would have a single log file for the whole day instead of multiple log files separated by few minutes
having it set as "year-month" would allow for at most 12 log files each year no matter how many restarts authelia goes through

Details

the side effect that may arise is that setting it to "minute" would probably mess up the purpose of logging, but I think that's an issue of the user that has specified it like that

Documentation

No response

Pre-Submission Checklist

• I agree to follow the Code of Conduct

• I have checked for related issues and checked the documentation