This specifies an optional Perl hook that runs for each log
message when defined. The hook must return the formatted log message. By
default, no hook is defined and LogFormat or the
default format is used. The hook parameters are the following:
Message severity (integer)
Log message
Reference to the current request
Tracing identifier (string)
See goodies/logformat.cfg for a sample
configuration file with JSON and CEF (ArcSight Common Event Format)
formats.
Note
Consider installing JSON::XS for higher performance JSON
encoding.
