POST /objectives returns the new object's id
POST /objectives returns 400 if no objective params
POST /objectives returns 401 if invalid data
GET /objectives returns 200
GET /objectives returns the json representation of all objectives
GET /objectives/:id returns status code 200
GET /objectives/:id returns the json representation of the intended object
GET /objectives/:id returns 400 if no such objective
PUT /objectives returns status code 200
PUT /objectives/:id updates the entry in the database
PUT /objectives returns 400 if no such objective
PUT /objectives/:id returns 401 if no objective data is given
PUT /objectives returns 401 if the entry is invalidated
DELETE /objectives/:id removes the objective from the database
DELETE /objectives/:id returns 400 if no such objective