Add ignore_advertisement in leafnode config to ignore advertised remotes

[acormier-maia]

Proposed change

Add ignore_advertised_remotes in leafnode configuration block (defaults to false) which only affects the leafnodes. Adding this option will ignore any ip addresses advertised by the hub.

leafnodes {
  ignore_advertised_remotes: true,
  remotes [
    {
      urls: ["tls://example:7422"]
      tls: {
         handshake_first: true
         # other TLS fields...
      }
    }
  ]
}

Looking for feedback on the naming.

Use case

Currently, there is no way to prevent the leaf nodes from receiving (and attempting to use) advertised IPs from the Nats hub servers. In our deployment, those IPs that are advertised are internal docker IPs. The actual public IPs are not known by the servers since they are proxied).

We want to fully manage what hostname/ips the leaf nodes use to connect to the hub. This is not currently possible because the hub always advertises it's IP with no way to disable.

Contribution

Yes.