[Enhancement] Logging for Preauthenticated mode is difficult to enable

[thedoc31]

Is your feature request related to a problem? Please describe.
In #5656, a solution was posted to turn up logging in 3.x for the Preauthentication Request module. This involved adding a rundeck-config.groovy file in the Rundeck config path. This no longer works. As a result, an alternate method should be presented to users who need to debug this functionality.

Describe the solution you'd like
It took me a while to figure out, but I discovered you can now set this in log4j2.properties in your Rundeck config folder by adding the following lines.

logger.preauth.name = org.rundeck.security.RundeckPreauthenticationRequestHeaderFilter
logger.preauth.level = info
logger.preauth.additivity = false
logger.preauth.appenderRef.stdout.ref = STDOUT

For me, messages are written to service.log. I am not sure if that is standard or not for non-dockerized Rundeck.

I'm of the opinion that this should be in the default log4j2.properties but at error level so it doesn't make too much noise unless someone wants it to. I created this ticket as the basis of a PR I will submit for it.

Describe alternatives you've considered
N/A - there are no alternatives but leaving the logging out entirely, and it's a simple enough addition.

Additional context
Originally posted by @thedoc31 in #5656 (comment)