Create API endpoints for DB interactions

With unit tests

[x] Retrieve a specific user: GET /api/users/:id
[x] Create a new user: POST /api/users
[x] Update a user: PUT /api/users/:id
[x] Delete a user: DELETE /api/users/:id
[x] Retrieve all personality types: GET /api/personality_types
[x] Retrieve a specific personality type: GET /api/personality_types/:id
[x] Create a new personality type: POST /api/personality_types
[x] Update a personality type: PUT /api/personality_types/:id
[x] Delete a personality type: DELETE /api/personality_types/:id
[x] Retrieve all favorites: GET /api/favorites
[x] Retrieve favorites for a specific user: GET /api/favorites?user_id=:user_id
[x] Retrieve favorites for a specific song: GET /api/favorites?song_id=:song_id
[x] Add a new favorite: POST /api/favorites
[x] Remove a favorite: DELETE /api/favorites/:id
[ ] Retrieve recommendations for a specific user: GET /api/recommendations?user_id=:user_id
[ ] Retrieve recommendations for a specific song: GET /api/recommendations?song_id=:song_id
[ ] Add a new recommendation: POST /api/recommendations
[ ] Remove a recommendation: DELETE /api/recommendations/:id

JamesRobertSutcliffe / personality-music-recommender