Update Rails application to use redis-db-load-balancing

Requirements:

  • Add new instance of Gitlab::Redis::DbLoadBalancing
  • Use the new instance of Gitlab::Redis::DbLoadBalancing
    • To be used in lib/gitlab/database/load_balancing/sticking.rb
    • Introduced via MultiStore feature flags to migrate the data naturally.
  • Add the db_load_balancing instance in config/README.md
Edited by Alejandro Rodríguez