Get aggregated time spents for given person and month.
GET /data/persons/{person_id}/time-spents/month/{year}/{month}
curl \
-X GET http://api.example.com/data/persons/{person_id}/time-spents/month/{year}/{month}
curl \
-X GET http://api.example.com/data/persons/{person_id}/time-spents/month/{year}/{month}