Resolve all TODOs in the codebase

[ketphan02]

This accidentally merged #131

Resolve 2 issues:

• config.jest.js is having an error saying there's no babel-jest
• Loaded types are not import type -> make the source heavier
• hash functions are not designed in a preferable way

Resolve TODOs:

• Make sure DIFFICULT_LIST matches with the database's difficulties: RESOLVED ✅ by loading the type directly from the @prisma/client.
• Create failed tests (and similars): UNRESOLVED ❌ because have no time and this is very time-consuming.
• Age-related TODOs: UNRESOLVED ❌ because waiting for add-birth-year to be merged.
• Create Header for admin page: RESOLVED ✅ by Admin header #121 (if got merged)
• Convert bool to string: RESOLVED ✅ by using regex.

• Calculate success rate of the submissions: RESOLVED ✅ with a new service and some implementation.
• Save session to db (and local storage): UNRESOLVED ❌ because lack of time to implement.
• Link to view on map: UNRESOLVED ❌ because lack of time to implement and no relative url in the view map.
• Properly handle truncations (i.e. the ... at the end of sliced strings): UNRESOLVED ❌ because lack of time to implement.
• Should be an alert dialog w/ link to login page: UNRESOLVED ❌ because lack of time to implement.