Restricting topics to username ?

[Deadman69]

Hello,

I would like to limit my usergroup "user" to access only their specific topic using dynamic-security.json
I have tried something like this

{
  "rolename": "user",
  "acls": [
    {
      "acltype": "publishClientSend",
      "topic": "agents/${username}",
      "priority": 0,
      "allow": true
    },
    {
      "acltype": "publishClientReceive",
      "topic": "agents/${username}",
      "priority": 0,
      "allow": true
    },
    {
      "acltype": "subscribePattern",
      "topic": "agents/${username}",
      "priority": 0,
      "allow": true
    },
    {
      "acltype": "unsubscribePattern",
      "topic": "agents/${username}",
      "priority": 0,
      "allow": true
    }
  ]
}

But it seems this is not possible. I have tried to search for documentation on this subject but i couldn't find anything.

I could create a group for each user restricting to agents/xxxxxxxx but I don't think it would be a good strategy since I will need (at least) a few thousands clients.
Having a group being able to restrict users to their username would be better than creating a lot of groups for me.

Is it possible or should I just allow all my users to read everything and encrypt my messages ? (I am on a semi-public infrastructure).

Thanks