added support for REDIS_CACHE_URL

Author: damianlegawiec

.env.example

@@ -2,6 +2,7 @@
 SECRET_KEY_BASE=change-me-generate-with-bin-rails-secret
 DATABASE_URL=postgres://postgres@localhost:5432/spree_production
 REDIS_URL=redis://localhost:6379/0
+# REDIS_CACHE_URL=redis://localhost:6380/0  # dedicated cache Redis (falls back to REDIS_URL)
 
 # Web Server
 PORT=3000

config/environments/production.rb

@@ -53,9 +53,11 @@
   # Don't log any deprecations.
   config.active_support.report_deprecations = false
 
-  # Use Redis for caching if REDIS_URL is set, otherwise fall back to memory store.
-  if ENV["REDIS_URL"].present?
-    config.cache_store = :redis_cache_store, { url: ENV["REDIS_URL"] }
+  # Use Redis for caching. REDIS_CACHE_URL allows a dedicated cache Redis,
+  # falling back to REDIS_URL (shared with Sidekiq) if not set.
+  redis_cache_url = ENV["REDIS_CACHE_URL"] || ENV["REDIS_URL"]
+  if redis_cache_url.present?
+    config.cache_store = :redis_cache_store, { url: redis_cache_url }
   else
     config.cache_store = :memory_store
   end