Use Redis as the SignalR backplane

[stewartanderson3]

• Setup backend to use Redis as the backplane.

• Configure SignalR (backend) to only allow web sockets

• Configure SignalR npm client to skip negotiation and just use web sockets. Otherwise sticky-sessions are required (see second link below).

• https://docs.microsoft.com/en-us/aspnet/core/signalr/redis-backplane?view=aspnetcore-5.0

• https://docs.microsoft.com/en-us/aspnet/core/signalr/scale?view=aspnetcore-5.0#sticky-sessions