Add support for SignalR hubs requiring authorization

[PerfectlyNormal]

Not really happy with the error handling in SignalRClientEndpoint.BuildListenerAsync. Since we try connecting immediately any errors prevents us from starting. The most common error will (probably) be unauthorized, so catching and logging that. But there's probably a lot better ways of handling this.

SignalR expects a Func<Task<string?>> as a token provider. I wrapped that so we get access to the IServiceProvider to get configuration or anything like that. That turns into a Func<IServiceProvider, Func<Task<string?>>> which isn't very pretty.

Feel free to edit or suggest improvements

[jeremydmiller]

@PerfectlyNormal One thing at a time. Let's go w/ what you've done and just collect feedback from users.