Use Redis for cache on Heroku demo.

config/packages/demo/cache.yaml

@@ -0,0 +1,22 @@
+framework:
+    cache:
+        # Unique name of your app: used to compute stable namespaces for cache keys.
+        prefix_seed: Part-DB/Part-DB
+
+        # The "app" cache stores to the filesystem by default.
+        # The data in this cache should persist between deploys.
+        # Other options include:
+
+        # Redis
+        app: cache.adapter.redis
+        default_redis_provider: '%env(REDISCLOUD_URL)'
+
+        # APCu (not recommended with heavy random-write workloads as memory fragmentation can cause perf issues)
+        #app: cache.adapter.apcu
+
+        # Namespaced pools use the above "app" backend by default
+        pools:
+            # Here all things related to cache the tree structures
+            tree.cache:
+                adapter: cache.app
+                tags: true