Add readiness review for cache in redis-cluster
What
Readiness Review doc for moving our cache
Redis database to Redis Cluster.
Readiness Review issue: #75 (closed)
The readiness review references the existing https://gitlab.com/gitlab-com/gl-infra/readiness/-/blob/master/redis-cluster/ratelimiting.md updated to reflect the cache workload which has a lower failure tolerance and higher load compared to rate-limiting.
Why
Provides horizontal scalability.
Implementation epic: &878 (closed)
Edited by Sylvester Chin