Allow UNIX timestamp auth

[GaraQuor]

Hello,

It would be great if we could pass a raw UNIX timestamp in the auth header.
A simple solution is to pass an '@' at the beginning of the value to strtotime treat the input as a UNIX timestamp (as described here https://www.php.net/manual/en/datetime.formats.compound.php)

The only fix is to add '@' char in the sanitizer allowed array

[ndejong]

Cool, added to the "enhancements" list