Create Custom CategoryTypes

Users should have the ability to create, edit, read, and delete a set of categories - storing them in enum type should be best for now.
This way the DB can store a numeric data type and the backend can easily convert that to an enum.
Or maybe have their own Dto with an ID?
We can discuss the data type of how to store Category types

1. Create new category table definition for DB
2. Plan how to connect it to Users and CashflowEntries in DB
3. Create CategoryTypes Controller
4. Create CategoryTypes repository in backend