Implement `prune()` strategy

[Hobadee]

We should implement a prune() strategy to remove any orphaned items.

This will be a dangerous function to use, but very important for more advanced workflows or cleanups. This function should generally work as follows:

1. Take a list of objects as input. (List A) We presume this will be a scan of the originating endpoint, but could be something else.
2. Scan the endpoint to be pruned and create a list of objects (List B)
3. For all items in List A, remove that item from List B
4. Remove all items remaining in List B from the endpoint to be pruned