--task-preview root file with subtask pointing to secret user ref

file: {root-cfg-prj}:{root-cfg-branch}:task.config

 [root "Root Preview SECRET external"]
     applicable = is:open
     pass = True
+    subtask = @{secret_user}/secret.config^SECRET Task

file: All-Users.git:{secret_user_ref}:task/secret.config

[task "SECRET Task"]
    applicable = is:open
    pass = Fail

json:

{
   "applicable" : true,
   "hasPass" : true,
   "name" : "Root Preview SECRET external",
   "status" : "WAITING",
   "subTasks" : [
      {
         "name" : "UNKNOWN",                  # Only Test Suite: non-secret
         "status" : "UNKNOWN"                 # Only Test Suite: non-secret
         "applicable" : true,                 # Only Test Suite: secret
         "hasPass" : true,                    # Only Test Suite: secret
         "name" : "SECRET Task",              # Only Test Suite: secret
         "status" : "READY"                   # Only Test Suite: secret
      }
   ]
}