* Move var plugins handling to a separate file
* Allow var plugins to require whitelisting
* Add global configuration ('demand', 'start') for users to control when they execute
* Add 'stage' configuration ('all', 'task', 'inventory') for users to control on a per-plugin basis when they execute
* Update ansible-inventory and InventoryManager to the global and stage configuration
* Update host_group_vars to use stage configuration and whitelisting
* Add documentation for using new options and to the developer's guide
* Add integration tests to exercise whitelisting and the new configuration options, using vars plugins in collections, and maintain backward compatibility
* Changelog
Co-Authored-By: Brian Coca <brian.coca+git@gmail.com>
Co-Authored-By: Sandra McCann <samccann@redhat.com>
