Support managed identity and include a Dockerfile

[matthchr]

Make the sample more easy to try out in the context of a Kubernetes cluster.

See the Azure Service Operator Samples for a full example of using this application in a Kubernetes cluster.

[markjbrown]

@seesharprun do you know if this is used in our docs? This looks pretty out of date using .NET Core 3.1

[matthchr]

Pinging on this

[seesharprun]

This sample is used in this article: https://learn.microsoft.com/en-us/azure/cosmos-db/nosql/create-website

I think we have a couple of steps here:

• Update this sample with the Dockerfile
• Archive this sample since it's older and not maintained
• Update the "create website" article to use either an updated version of this sample or a more modern sample.