Things to refactor before handoff

• abstract out method isManager
• consider consolidating types and validators into one file for the sake of maintaining code organization
• change type naming convention to PascalCase instead of ALL_CAPS since the latter generally implies constant
• code could (optionally) be reorganized (a lot of files in backend/src could be put inside config)
• certain methods and classes could be better named (instead of NudgeServiceImpl call it NudgeService, and call the interface NudgeServiceProps)