You must have docker and docker-compose installed on your computer
from the root of the project execute the following commands in order
docker-compose up -d --build
docker exec -it mongodb bash
mongo -u root -p root
db.getSiblingDB ('challenge'). createUser ({user: 'root', pwd: 'root', roles: [{role: 'readWrite', db: 'challenge'}]});
wait 5-10 seconds
that's for user creation, after that you can already quit the bash and use the API