Add more config variables for transit-unsealing and raft-joining

[gw0]

Currently, the Vault configuration (/tmp/storageconfig.hcl) only provides HOST_IP and POD_IP as variables that get replaced. Additionally, the used sed commands are not well written and can not support entering URLs (or anything that contains a /).

This two variables are not enough to set up Vault correctly in all scenarios (in HA you need API_ADDR). For unsealing with Vault Transit (docs) you also need to configure the address of another Vault server (eg. TRANSIT_ADDR). And to set up Raft backend (docs) as easy as possible it is beneficial, that all nodes attempt to automatically join the cluster (eg. RAFT_ADDR). With this PR these can all be set as environment variables under extraEnvironmentVars: and this enables you to utilize variables in Helmfile (or other wrappers on top of Helm).

Anyway, I have been successfully using and redeploying Vault with transit-unsealing and raft-joining for a couple of months now with this PR and such a configuration:

      config: |
        ui = true
        api_addr = "API_ADDR"
        cluster_addr = "https://POD_IP:8201"
        listener "tcp" {
          address         = "[::]:8200"
          cluster_address = "[::]:8201"
        }
        storage "raft" {
          path = "/vault/data"
        }
        seal "transit" {
          address         = "TRANSIT_ADDR"
          disable_renewal = "false"
          key_name        = "unseal_key"
          mount_path      = "transit/"
        }

[jasonodonnell]

Thanks for the contribution @gw0!

We'd like to merge these transit values, however, the auto-join code needs to be removed. There's a feature coming to Vault in the near future that will allow auto-join which we plan to utilize in this project.

[gw0]

I am closing this PR in favor of #398 that contains only the improved handling of environment variables and adds the TRANSIT_ADDR env variable. The option of running extra commands was in the meantime super-seeded with the postStart lifecycle hook and the vault.command macro.