Grok pattern COMMONAPACHELOG fails to parse the REMOTE_USER (%u) if it is in email address format

[https://httpd.apache.org/docs/2.4/mod/mod_log_config.html#formats](url) defines %u as _Remote user if the request was authenticated. May be bogus if return status (%s) is 401 (unauthorized)._

The Apache docs do not specify a particular format for the user name.

The Grok pattern is defined as:
%{IPORHOST:clientip} %{HTTPDUSER:ident} %{USER:auth} \[%{HTTPDATE

The bit dealing with %u is %{USER:auth} which is further defined as:
USER %{USERNAME}
USERNAME [a-zA-Z0-9._-]+

So the current Grok for _auth_ will fail to parse an auth field in the form of an email address due to the @ symbol

HTTPDUSER is defined as: %{EMAILADDRESS}\|%{USER}

If you substitute HTTPDUSER instead of USER then it will parse OK for both email addresses and usernames without @ in them.