create sync endpoint/websocket for sync

[githubbob42]

Mingle Card: 2447
See #2439 for story details.

Task

Create a new sync endpoint (or websocket) for initializing long-running sync downloads. The endpoint itself will not perform any of the interaction with SFDC - it should simply insert a sync request into a queue for later processing.

The sync request should contain:

• oauth token (which contains the user id and org id)
• timestamp when the sync request was made
• correlation id (perhaps the socket id if using web sockets) to coordinate the response with the original request (or with the original websocket)

Using socket.io and mongodb-queue, this might look like this:

 // when a connection to the client is made

  io.on('connection', function (socket) {

   // subscribe to the client syncing

    socket.on('SYNC\_GET', function(data, ack) {

      var session \= socket.handshake.session,

          oauth \= session.oauth;

     // add the sync request to the queue

      queue.add({ oauth: oauth, timestamp: new Date(), correlationId: socket.id }, function(err, id) {

        // notify the client of any errors adding to the queue so they can try again

        if(err) socket.emit('status', { error: err });

        // when the item is safely in the queue, notify the client

        if(ack && !err) ack();

      });

    });

  });

[githubbob42]

Story: #2196 User initiates a sync request on the client (Mingle)