use case: after some plugin has been released and used in the field for some time, we realize that the resource key doesn't uniquely identify resources as well as we thought it would...to the extent X different resources are discovered as a single resource instance, suppressing X-1 of them.

so, if we enhance the plugin to use a better resource key, then we have the issue that any pre-existing resources using the old key will be orphaned. since resource key is the mechanism by which we match up existing, server-side persisted resources with agent-side discovered resources during the inventory sync/merge process. so, it would be nice if there existed a mechanism to improve resource key uniqueness for customers that need additional uniqueness per agent, but which kept the existing resources already in inventory working.

a quick strategy, not to difficult to implement would be:

* add optional getPreviousKey to the api
** if previousKey != null && previousKey != newlyDiscoveredKey && previousKey == persistedKey, then update persisted key to use newly discovered key