service: Add support for redis

roles/service/meta/argument_specs.yaml

@@ -189,6 +189,13 @@ argument_specs:
           - Required if service_database_type is postgres, does nothing otherwise
         type: str
         required: false
+      service_redis:
+        description: >-
+          Whether to install redis in a container accessible to the service at host
+          {{ service_name }}-redis.
+        type: bool
+        required: false
+        default: false
 
       service_additional_containers:
         description: