add support for sharding

[chicco785]

it would be nice to support sharding. relevant information and examples can be found at the following links:

• https://docs.mongodb.com/manual/sharding/
• https://stackoverflow.com/questions/41815916/docker-with-mongodb-3-4-replica-shard
• https://github.com/jfollenfant/mongodb-sharding-docker-compose
• https://github.com/singram/mongo-docker-compose/blob/master/docker-compose.yml

we should check if it is possible to have 2 instances of replicaset controller, one for the shards, and one for the configuration servers