Add more configuration options for redis

- `REDIS_HOST` can be specified in the secrets
- Two new secrets: `REDIS_PASSWD` and `REDIS_DB`

cof/settings/common.py

@@ -22,7 +22,8 @@ except KeyError:
 # Other secrets
 try:
     from .secret import (
-        SECRET_KEY, RECAPTCHA_PUBLIC_KEY, RECAPTCHA_PRIVATE_KEY, ADMINS
+        SECRET_KEY, RECAPTCHA_PUBLIC_KEY, RECAPTCHA_PRIVATE_KEY, ADMINS,
+        REDIS_PASSWD, REDIS_DB, REDIS_HOST
     )
 except ImportError:
     raise RuntimeError("Secrets missing")
@@ -159,7 +160,10 @@ CHANNEL_LAYERS = {
     "default": {
         "BACKEND": "asgi_redis.RedisChannelLayer",
         "CONFIG": {
-            "hosts": [(os.environ.get("REDIS_HOST", "localhost"), 6379)],
+            "hosts": [(
+                "redis://:{}@{}:6379/{}"
+                .format(REDIS_PASSWD, REDIS_HOST, REDIS_DB)
+            )],
         },
         "ROUTING": "cof.routing.channel_routing",
     }