Lock contention when processing large volume of REST API requests

The following stack trace was identified as a bottleneck when running performance tests:

This write lock is invoked in the path of validating user credentials and creates a source of contention for Jetty's worker threads: https://github.com/OpenNMS/opennms/blob/opennms-28.1.1-1/opennms-config/src/main/java/org/opennms/netmgt/config/UserManager.java#L1177

Overview of system threads: