Update ratelimit.py docstring; add Redis service to docker-compose

ratelimit.py: fix module docstring to reflect current _NAMESPACE resolution
  (settings.POD_NAMESPACE, not K8s SA files read inside the middleware).

docker-compose.yaml:
  - Add saplredis service (redis:7-alpine, no persistence, 512 MB maxmemory,
    allkeys-lru, 4 databases, same policy as k8s ConfigMap).
  - Add REDIS_URL=redis://saplredis:6379 and CACHE_BACKEND=redis to the
    sapl service so local docker-compose runs use Redis out of the box.
  - sapl depends_on now includes saplredis.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker/docker-compose.yaml

@@ -18,6 +18,7 @@ services:
       - "5433:5432"
     networks:
       - sapl-net
+
   saplsolr:
     image: solr:8.11
     restart: always
@@ -32,6 +33,34 @@ services:
       - "8983:8983"
     networks:
       - sapl-net
+
+  saplredis:
+    image: redis:7-alpine
+    restart: always
+    container_name: redis
+    labels:
+      NAME: "redis"
+    command: >
+      redis-server
+      --save ""
+      --appendonly no
+      --maxmemory 512mb
+      --maxmemory-policy allkeys-lru
+      --maxmemory-samples 10
+      --maxclients 1000
+      --timeout 300
+      --tcp-keepalive 60
+      --hz 20
+      --lazyfree-lazy-eviction yes
+      --lazyfree-lazy-expire yes
+      --lazyfree-lazy-server-del yes
+      --databases 4
+      --protected-mode no
+    ports:
+      - "6379:6379"
+    networks:
+      - sapl-net
+
   sapl:
     image: sapl:local
 #    build:
@@ -57,20 +86,25 @@ services:
       IS_ZK_EMBEDDED: 'True'
       ENABLE_SAPN: 'False'
       TZ: America/Sao_Paulo
+      REDIS_URL: redis://saplredis:6379
+      CACHE_BACKEND: redis
     volumes:
       - sapl_data:/var/interlegis/sapl/data
       - sapl_media:/var/interlegis/sapl/media
     depends_on:
       - sapldb
       - saplsolr
+      - saplredis
     ports:
       - "80:80"
     networks:
       - sapl-net
+
 networks:
   sapl-net:
     name: sapl-net
     driver: bridge
+
 volumes:
   sapldb_data:
   sapl_data:

sapl/middleware/ratelimit.py

@@ -16,11 +16,12 @@ Decision flow (per request):
 All decisions are no-ops when RATELIMIT_DRY_RUN=True (logged only).
 Degrades gracefully to non-atomic counting when Redis is unavailable.
 
-Tenant namespace (_NAMESPACE) is resolved once at module load from:
-  1. POD_NAMESPACE env var  (K8s Downward API — preferred)
-  2. K8s service-account namespace file (always present in-cluster)
-  3. 'global' (local development fallback)
-Since each pod serves exactly one tenant, this is a startup constant —
+_NAMESPACE is settings.POD_NAMESPACE, resolved once at startup:
+  - K8s: start.sh reads the k8s namespace from the Downward API env var
+    or the service-account namespace file, writes it to .env as POD_NAMESPACE.
+  - Bare-metal / VM / docker-compose: defaults to the machine hostname
+    (socket.gethostbyname_ex result computed in settings.py).
+Since a deployment serves exactly one tenant, this is a startup constant —
 no per-request lookup is needed or correct.
 """