Using systemd entry in record_modifier

I'm not sure I'm phrasing my question correctly, but the idea of what I'm trying to achieve is this:

```
<filter systemd.**>
  @type record_modifier
  <record>
    service $NameOfASystemdServiceFromTheEntry
  </record>
</filter>
```

so `service` key would `docker.service` or `ntp.service` or whatever service actually produced the log entry. Is this possible?