Filebeat MySQL slowlog module - user.name exists and related.user field missing

[leweafan]

Describe the enhancement:

Filebeat MySQL slowlog module missing related.user field.

According to field description:

All the user names or other user identifiers seen on the event

The problem not only with this one module. Seems like here is no autotest to check related.user in case user.name field exists.
Created feature request to add the autotest for this case.

Describe a specific use case for the enhancement or feature:

Check mariadb-10.3.13.log-expected.json - user.name field exists and related.user missing.

[botelastic]

This issue doesn't have a Team:<team> label.