Helm chart is lacking functionality to mount volumes and secrets #163

Add customizable environment and volume options, specifically, extraEnv, extraEnvFrom, extraVolumes, and extraVolumeMounts to allow flexible configuration and secure secret injection.

Make it possible to populate secrets (such as redis password) from k8s secrets (fits nicely with terraform + external secrets operator)

Make it possible to mount the Google Memstore (Redis) CA into the container (Google Memstore Redis is per instance, so every Redis you have you have a different CA cert you need to use, lame but that's how Google has implemented it.

Addressed by #162