NAT session logging

This feature provides the ability to enable session open and close logs from the CLI. This is a continuation of the work done as part of logging infrastructure improvements. The infrastructure facilitates better control of what logs are generated. 

To configure NAT session logging for a service set: 

• Include the class nat-logs statement at the [edit services service-set service-set-name syslog host host-name] hierarchy level. 
• Include the class session-logs open | close statement at the [edit services service-set service-set-name syslog host host-name] hierachy level. By default, session open and close logs are produced. Specify open to receive only session open logs, or close to receive only session close logs. 

Use the show services service-sets statistics syslog detail command to display information about collected log information.