Calling methods on hub from client should be supported if serverless signalR service has upstream configured

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The documentation reads:
Note
Calling hub methods from a client is only supported when using the Azure SignalR Service in Default mode. For more information, see Frequently Asked Questions (azure-signalr GitHub repository).

-1- the link to the FAQ has moved.
-2- in the FAQ we read:
Can I send message from client in serverless mode?
You can send message from client if you configure upstream in your SignalR instance. Upstream is a set of endpoints that can receive messages and connection events from SignalR service. If no upstream is configured, messages from client will be ignored.
For more information about upstream see this doc.
Upstream is currently in public preview.

So it seems it it is out of date.
An example calling hub methods from the client would be welcome. The only one i could find is the bidirectional chat at https://github.com/Azure/azure-functions-signalrservice-extension/tree/master/samples/bidirectional-chat which seems overly complicated, requires authentication, etc. ax example with plain javascript (not requiring additioanl libraries) and that could run in the signalR emulator would be preferred so we would not need to setup CORS, etc

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* ID: 3cf283c9-5cd2-a9ff-b8c8-372d8a04356d
* Version Independent ID: 729fddcf-24e4-b563-4952-a8045b231868
* Content: [ASP.NET Core SignalR JavaScript client](https://docs.microsoft.com/en-us/aspnet/core/signalr/javascript-client?view=aspnetcore-3.1)
* Content Source: [aspnetcore/signalr/javascript-client.md](https://github.com/dotnet/AspNetCore.Docs/blob/master/aspnetcore/signalr/javascript-client.md)
* Product: **aspnet-core**
* Technology: **aspnetcore-signalr**
* GitHub Login: @bradygaster
* Microsoft Alias: **bradyg**