Investigate if website back end can be just SignalR as a Service

[nzthiago]

Event Grid supports mapping: https://docs.microsoft.com/en-us/azure/event-grid/input-mappings

and SignalR is now offered as a Service: https://azure.microsoft.com/en-us/blog/azure-signalr-service-a-fully-managed-service-to-add-real-time-functionality/

Could these be used to replace the web backend? This combined with #3 would make the whole sample 'serverless'

[nzthiago]

Even if we don't remove the site backend entirely, this would be better for scalability too.