Add secret store choice input

Author: seunghun1ee

.github/workflows/stackhpc-multinode.yml

@@ -25,6 +25,13 @@ name: Multinode
         options:
           - ovn
           - ovs
+      secret_store:
+        description: Secret store to use as Certificate Authority
+        type: choice
+        default: openbao
+        options:
+          - openbao
+          - vault
       upgrade:
         description: Whether to perform an upgrade
         default: none