It is not possible to filter Audit log records by user "System"

Problem description: It is not possible to filter the records in Reports => Audit log view by user "System", therefore it is not possible to view only server performed operations.

Steps to reproduce:

1. Perform autoregistration, network discovery or discover entities using LLD
2. Navigate to Reports => Audit log
3. Attempt to filter the audit log so that only actions performed by the server would be displayed (filter by user = System).

Result: it is not possible because user System is not present in the list of users.
Expected: there should be some way to view only server performed actions in theaudit log view.