* fix issue with incorrect user detection when Invoking for User
* fix failed testcases
* use proper extension method to avoid potential null reference exception
* fix for channel name in redis version + follow SignalR team recommendations
* remove unncessary freespace
* remove whitespaces
* introduce IUserIdProvider to resolve user id
* Move IUserIdProvider from HubLifetimeManager to HubConnectionContext
* setting user id to connection context in hubendpoint
* Added Cancellation support
- Added ConnectionAbortedToken to the HubConnectionContext. This allows
arbitrary code to access a handle that represents the connection lifetime
without handling OnDisconnectedAsync on the hub itself.
- Expose Abort on HubConnectionContext to allow server side methods to
abort the connection.
- Use the Abort to stop the main loop when unexpected invocation errors happen.
- Use the connection aborted token as unsubscribe from the IObservable and to complete
the IAsyncEnumerator for streaming results.