Compose REDIS_URI from component parts.

This updates the configuration handling for the Redis connection string.
The motivation is so that the Redis password can be managed separately
via Azure Key Vault and eventually be rotated independently of the rest
of the connection URI.

This also tweaks the method we use to build the DATABASE_URI and removes
some stale config from the CI config file.

deploy/azure/atst-envvars-configmap.yml

@@ -7,14 +7,16 @@ metadata:
 data:
   ASSETS_URL: https://atat-cdn.azureedge.net/
   BLOB_STORAGE_URL: https://atat.blob.core.windows.net/
-  CELERY_DEFAULT_QUEUE: celery-master
   CDN_ORIGIN: https://azure.atat.code.mil
+  CELERY_DEFAULT_QUEUE: celery-master
   CSP: azure
   FLASK_ENV: master
   LOG_JSON: "true"
   OVERRIDE_CONFIG_FULLPATH: /opt/atat/atst/atst-overrides.ini
   PGSSLMODE: verify-full
   PGSSLROOTCERT: /opt/atat/atst/ssl/pgsslrootcert.crt
+  REDIS_HOST: atat.redis.cache.windows.net:6380
+  REDIS_TLS: "true"
   STATIC_URL: https://atat-cdn.azureedge.net/static/
   TZ: UTC
   UWSGI_CONFIG_FULLPATH: /opt/atat/atst/uwsgi.ini