Add Aether cluster and app configs

Change-Id: I1394ca5690267e930bc74eb2602c0473c8d60c1b
diff --git a/deployment-configs/aether/apps/staging-cassandra.yaml b/deployment-configs/aether/apps/staging-cassandra.yaml
new file mode 100644
index 0000000..00fbdde
--- /dev/null
+++ b/deployment-configs/aether/apps/staging-cassandra.yaml
@@ -0,0 +1,9 @@
+fullnameOverride: "cassandra"
+image:
+  tag: "2.1.20"
+persistence:
+  enabled: true
+  storageClass: "zonal-ssd"
+config:
+  cluster_domain: "staging.central"
+  endpoint_snitch: "GossipingPropertyFileSnitch"