Add Raft HA support

[jasonodonnell]

This adds a new HA option, raft, for the upcoming Vault 1.4 release. This makes the following changes:

• Creates a new headless service required to allow the pods communicate directly with each other
• Lifts limitations on HA mode not creating PVCs for storage
• Adds new configurations specifically for Raft.

helm install vault \
  --set='server.ha.enabled=true' \
  --set='server.ha.raft.enabled=true' .

Once deployed you can initialize vault-0 and unseal:

# Note: vault-0 is going to be our leader initially.
kubectl exec -ti vault-0 -- vault operator init
kubectl exec -ti vault-0 -- vault operator unseal

Next, for each other vault pod, join the raft cluster and unseal:

kubectl exec -ti <NAME OF POD> -- vault operator raft join http://vault-0.vault-internal:8200
kubectl exec -ti <NAME OF POD> -- vault operator unseal

After logging into Vault using a token, you can check the configuration of Raft:

kubectl exec -ti vault-0 -- vault login
kubectl exec -ti vault-0 -- vault operator raft configuration -format=json

Or using status:

kubectl exec -ti vault-0 -- vault status

[tvoran]

I feel like this could use some comments about how/when to use raft, and/or maybe updating the comments above ha:.

[jasonodonnell]

Addressed!