Improve insecure domain notification

When I try to access code-server over a local network I get an error message
```code-server is being accessed over an insecure domain```
I understand that the recommended method to expose the server is either SSH or reverse proxy. All these methods are an overkill if the server is always behind the same firewall as the client. There should be a way to acknowledge the message and dismiss it permanently. I did not notice any broken functionality despite the warning.