The use case is:

1. Specifically about security and NOT resource utilization
2. Specifically about interactive client connections (not sessions or transactions): a human being using mongo shell

This feature would also require a new field with a Role: interactiveIdleConnectionTimeout: <seconds>

User Story:
As a DBA, I need to prevent users from (accidentally) leaving authenticated shells connected to my critical databases open on their desktop/laptop. This is related to global security requirements at my company, which apply to all software we use.