Provide request attribute to hold username

Work done in NXP-32019 sets the principal name as HTTP session attribute to make it available in the tomcat's access.log pattern under

%{user_name}s

However, calls made with curl and basic authentication do not have a session scope and

%{user_name}s

would return nothing.

We should in addition set the principal name as HTTP request attribute to make it available under

%{user_name}r

https://tomcat.apache.org/tomcat-9.0-doc/config/valve.html