Integrate Redis into Authservice

Redis is required for HA Authservice

• Add dependency for Big Bang Redis
• Reference Argo MR
  • kpt the 12.8.3-bb.0 tag for redis into chart/external
  • change the dependency to reference the external folder.

- name: redis
  version: 12.8.3-bb.0
  repository: file://external
  alias: redis-bb

• Run helm dep update chart from the top level
• Redis has imagepullsecrets configured for private-registry by default, so no configuration should be needed there.
• Redis should be deployed without a password
• Configure each filter chain to know about redis:

https://github.com/istio-ecosystem/authservice/blob/c4e82ed739424043ffbebe927759dcd29429ed53/docs/README.md

redis_session_store_config	When specified, the Authservice will use the configured Redis server to store session data. Optional.	RedisConfig

This is currently blocked by dsop/istio-ecosystem/authservice#3 (closed)