Consider all string type system claims as user claims, rename and reconstruct in the SDK to avoid breaking changes to the customers
Special handling for "sub" claim, since "sub" claim is also used by SignalR as the UserId of the connection. Keep the first "sub" as it is, and rename other "sub" (if any) to user claims.
Fix https://github.com/Azure/azure-signalr/issues/1911 by: