Update how users are fetched, add a ton of unit tests for robustness

Migration completed to switch over to use the common account service to look up users as all required levers are now present. Additionally, the WorkingGroups service, api, and models have been removed as they aren't currently in use. When needed, they can be easily brought back in if needed.

Otherwise, a ton of basic testing was added to secondary classes and helpers to improve robustness of the project.