Integrate db permissions to deployment

[nkostoulas]

We need separate permissions for the API and the mainstay daemon. I created this https://github.com/commerceblock/mainstay/blob/develop/scripts/db-init.js months back but I think we should integrate it now to the mongo deployment.

Basically two separate roles. Service role should only be used by the mainstay daemon. The API role should be used by the node web backend. Nobody else should have access or we could introduce a third read only role.

Compose files should be updated with the new users.