structured logging

[wiese]

Currently the logfiles are not easy to parse, as they are not structured. Nowadays the logs are often JSON formated or key=value pairs separated by spaces.
JSON example line: {"level":"debug","time":"2023-12-07T08:03:47.162","sender":"SCP","message":"executed command \"/usr/local/bin/myHooks\", elapsed: 1.007732187s, error: <nil>"}

To facilitate the monitoring purposes with BNC, this should be introduced.
To discuss:

• as new log to not break existing workflows?
• new log with metrics only?
• write to port instead of file?
• ...

See #168 and #108.