Symmetric difference in set theory is used to determine which elements need to be added/removed to go from setA to setB. We use this atm when determining which roles are added/removed when changing a user's permissions.

This same logic can be applied to organization sync (WIP) and group sync (WIP). Felt better to just make it a generalized slice function. This code is slightly less efficient since a map was used before for membership, but the slices we are working with are small anyway.