Mongo child module for use with EKS

[thinkl33t]

Feature Request

Description of Problem:

As part of #327 we are building child modules for all legend dependencies. Mongo is one of these.

Potential Solutions:

Terraform child module that deploys a mongo container on top of a kubernetes cluster (EKS specifically but ideally this will be generic)

[thinkl33t]

Waiting for policy isn't a blocker - we'll build an initial deployment and modify it afterwards when the policy exists.

[eddie-knight]

Possible starting point: https://medium.com/@cramirez92/deploy-a-mongodb-replica-set-in-a-devops-fashion-style-infrastructre-as-code-f631d7a0ad80