Create API endpoints for getting, adding and deleting the preferences

[3nd3r1]

• GET /api/v1/users/preferences to get all the preferences of the user who did the request
• POST /api/v1/users/preferences to add a new preference to the user who did the request
• DELETE /api/v1/users/preferences to delete an existing preference of the user who did the request

[zlendo1]

Closed with #42