Allow connection only with confirmation

[freeconst]

In addition to authorized connections, it would be nice to add connection requests for privacy. Some x0vnc QueryConnect analog.

[any1]

There could be an option to call a user defined command upon connection, which would determine if the connection is accepted or not.

[lack]

Now that we have an IPC mechanism in wayvncctl, maybe this would be easier to do.

I'd suggest a new IPC command like event-receive that would register a client to be an auth-handler.

Then the client could expect to receive an auth-attempt IPC call, and would be expected to respond with a allow/disallow response.

Care must be taken to deal with the server's behavior with multiple IPC clients, and what to do in the event of nonresponse arriving.

[any1]

This is probably a good enough solution:

• The authentication method is configured in the config file or in a command line argument to wayvnc
• If the method is set to "query", we do the following:
• Generate a "client-auth-request" event when a client connects
• The event contains the user's submitted credentials.
• When an instance of wayvncctl receives this event, it calls wayvncctl client-auth-accept or wayvncctl client-auth-reject [reason]
• If the server does not receive an accept or reject command from wayvncctl within the timeout period, the client is rejected.