rig major updates

soleprint/station/cabinets/airflow/cabinet.json

@@ -7,7 +7,7 @@
   "rig_addon": "airflow",
   "ports": [8080],
   "volumes": ["airflow_logs"],
-  "depends_on": ["postgres", "redis"],
+  "depends_on": ["postgres"],
   "env": {
     "AIRFLOW_PORT": "8080",
     "AIRFLOW_ADMIN_USER": "admin",
@@ -15,8 +15,8 @@
     "AIRFLOW_DAGS_DIR": "./dags"
   },
   "notes": [
-    "Brings postgres and redis with it — Airflow needs a metadata database and a broker, and will not start without both.",
-    "LocalExecutor by default: one container, no separate worker. Switch to CeleryExecutor in service.yml when the room outgrows it.",
+    "Brings postgres with it — Airflow needs a metadata database and will not start without one. It gets its own `airflow` database on that instance, apart from the app's.",
+    "LocalExecutor by default: one container, no separate worker, no broker. redis is only needed to switch to CeleryExecutor in service.yml; add it then, not before.",
     "8080 collides with almost everything. Set AIRFLOW_PORT in the room's .env."
   ]
 }