Update log fields

This MR contains several minor improvements for the log fields:

• adds the namespace field to router logs (currently missing)
• record the user agent for audit logs: this should help us to identify if an action was performed from the Webservices portal, the OKD console or from the CLI)
• change the namespace_name field in container logs to namespace: this standardizes with the rest of the logs, allowing us to field all logs of a namespace with a single query (i.e. when searching for namespace: my-app we can immediately see event, audit, router and container logs.