Socket for run and start commands, and basic socket protocol

[beefon]

In this PR start and run commands are getting optional --start-socket-at CLI arg. If it is set, then socket is created at specified path.

New socket command allows you to send a JSON contents into socket. JSON has to conform CurieSocketRequest. Help for the command has some examples:

USAGE: curie socket --socket-path <socket-path> --socket-request <socket-request>

OPTIONS:
  -p, --socket-path <socket-path>
                          Opened unix socket of the container to interact with
  -r, --socket-request <socket-request>
                          Payload to send to socket (values: 
                              Ping the server example JSON: {"ping":{}}, 
                              Terminate the VM example JSON: {"terminateVm":{}}), 
                              Make screenshot example JSON: {"makeScreenshot":{"savePngImageAtPath":"\/path\/to\/output.png"}})
  -h, --help              Show help information.

I've also added 3 payloads, one is for testing (ping; i'm happy to remove it in case you don't like to have it around) and two with actual feature (terminating the VM and making screenshots).

Happy to split screenshot making feature to a separate PR if you want, but i found it rather small.

Example usage:

• Terminating VM

  ./.build/debug/curie socket -p /tmp/s.sock -r '{"terminateVm":{"waitToComplete": false}}'
  

• Making screenshot

  ../.build/debug/curie socket -p /tmp/s.sock -r '{"makeScreenshot":{"savePngImageAtPath":"\/Users\/beefon\/Desktop\/screenshot.png"}}'
  

I've tried to make UnixDomainSocketProtocol's JSON as human friendly as possible with extensibility for the future needs.

[marciniwanicki]

Big, big thanks @beefon! The changes look great. Left few small comments but overall it works well.

[marciniwanicki]

Maybe SocketServer and DefaultSocketServer to be aligned with the naming conventions of other utilities.

[marciniwanicki]

screenshotter var will be more aligned with other "VM" variable types, e.g. bundle not vmBundle.

[marciniwanicki]

Maybe in the future we can try to use async await.

[marciniwanicki]

What do we do with this result? Looks unused at the moment.

[beefon]

Currently it is used to provide feedback over socket whether VM has been terminated or failed, this is inside TerminateVmRequestProcessor:

            vm.terminateVmAndCurrentProcess(machineStateURL: vmBundle.machineState.asURL) { terminationResult in
                switch terminationResult {
                case .success:
                    settableResponse.set(response: .success([:]))
                case let .failure(error):
                    settableResponse.set(response: .error("Failed to terminate VM: \(error)"))
                }

                socketQueue.sync(flags: .barrier) {}
            }

[marciniwanicki]

Ah missed that, thank you.

[marciniwanicki]

Thank you @beefon for all the updates, you should be able to merge it now.

[beefon]