use MinIO for attachments

[jaredjennings]

https://docs.thehive-project.org/thehive/installation-and-configuration/architecture/3_nodes_cluster/

Not sure if we could use HTTPS for MinIO rather than HTTP - yet another trust store?

[jaredjennings]

Note that this only matters if you have more than one TheHive instance.

The clustering guide referenced is about manually setting up a Hive cluster. That isn't worth doing in Kubernetes. Akka documentation makes it seem like Akka can reach out for the right info. Those added smarts are a prerequisite for this work.