[BUGFIX] Use different field for logging in EXT:scheduler

The public method Scheduler::log accepts an optional $code as 3rd
parameter. Add this information to the parameter $details of
BackendUserAuthentication::writelog as otherwise it will be
casted to an integer and its information will be lost.

Resolves: #80592
Releases: master, 8.7
Change-Id: Iab5f1d285976e9e88795ebbe75faff9f689b1a8c
Reviewed-on: https://review.typo3.org/52846


Tested-by: TYPO3com <no-reply@typo3.com>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>