feat(rpc): automatically garbage collect observables + new event system + stats collection

• Fixed various soft memory leaks and hard to untangle circular references (making GC easier)

• All observables are now tracked via WeakRef and FinalizationRegistry, and frees them up on the server automatically when the client garbage collected them.

  • previously it was required that all clients unsubscribe from observables and subjects otherwise there will always be a state on the server for these objects. now, the client can just use the received observable/subject and once they are no longer used (garbage collected by the javascript engine) the rpc client detects it and frees the resources on the server automatically.

• Added new event system to track and control what the rpc kernel and connections do.
  onRpcConnection, onRpcConnectionClose, onRpcAction, onRpcAuth, onRpcControllerAccess

This not only allows to hook into various stages but also allows to replace RpcKernelSecurity for authentication and controller access:

const kernel = new RpcKernel();

kernel.listen(onRpcConnection, (event, logger: Logger) => {
    logger.log(`New Connection`);
});

kernel.listen(onRpcAction, (event, logger: Logger) => {
    logger.log(`action ${event.data.action}`, event.data.phase, event.data.timing);
});

kernel.listen(onRpcAuth, (event, logger: Logger) => {
    logger.log(`authenticating`);
    if (event.data.token === 'secret')  {
       event.data.session = new Session('Admin', '');
    }
});

kernel.listen(onRpcControllerAccess, (event, logger: Logger) => {
    logger.log(`authenticating`);
    if (event.data.session.username === 'Admin')  {
       event.data.granted = true;
    }
});

• Added statistics object RpcStats which collects statistics about the kernel, traffic, connections, actions, and observables.

const kernel = new RpcKernel();

kernel.stats.connections // currently active connections
kernel.stats.totalConnections // all handled connections so far

kernel.stats.actions
kernel.stats.incomingBytes
kernel.stats.outgoingBytes

kernel.stats.active.observables //how many active observables there are
kernel.stats.active.subscriptions //how many observable subscriptions there are
// and more

also each RpcKernelConnection has a stats object with the same data