OAIPMH Harvesting logging settings missing

**Describe the bug**
General logging level can be set through admin -> settings -Log level.
The OAIPMH harvester generates it own logging after each harvest run, which is not in the standard logging (stdin/sterr logging).
There is however no gui option to set the logging of the OAIPMH Harvester.
So e.g. I now have a harvester which gives no results, and the harvester does reflect that, but there is no setting to increase the log level so that I can inspect the url's sent by GN to the OAIPMH-server to see what went wrong.

**Desktop (please complete the following information):**
- FireFOX
-3.12.10
- Docker: geonetwork:3.12-postgres

Start by tracing the admin Settings > Log level configuration and the OAIPMH harvester's separate post-harvest logging path. No file or test is named, so identify where the GUI setting and harvester logging are connected; done means an administrator can control OAIPMH logging and inspect the requested URLs when a harvest produces no results.

Written by the indexing model from the issue text.