Refactor Factories

Description / Overview

Move current GradyUserFactory (currently in core.util.importer) to a seperate Factories file. To this file future factories can then be added. The reason for this is, that this factory (and future ones) are needed for easy creation of test data to test the api endpoints and should therefore not be part of importer.py file.

checklist

• Move GradyUserFactory to a new file Factories.py
• Make sure all files depending on the factory are updated accordingly