db test: refactor testCRUDCustomer()
db: refactor testCRUDSupplier()
db: refactor testCRUDProduct()
db: refactor testCRUDUser()
db: refactor testCRUDInvoice()
db: refactor testCRUDOrder()
db: refactor testCRUDDelivery()
db: refactor testAuthorizeUser()
db: finished refactoring

- reduced inter-dependancy between tests
- all tests pass even when run together now
Merge remote-tracking branch 'origin/master'