Application-gateway-kubernetes-ingress: Add support for configuring backend HTTP settings

[Jawshua]

Is your feature request related to a problem? Please describe.
There are a few settings that we currently have to manually configure after the backend settings have been created by the ingress. Primarily we need to enable connection draining and increase the request timeout, but I imagine the ability to configure the rest of the settings would come in handy for others.

Describe the solution you'd like
The nginx Ingress handles this with annotations, for example:

---
kind: Ingress
apiVersion: extensions/v1beta1
metadata:
  name: example
  annotations:
    kubernetes.io/ingress.class: "nginx"
    nginx.ingress.kubernetes.io/proxy‑connect‑timeout: 30

I imagine this could be handled in a similar fashion:

---
kind: Ingress
apiVersion: extensions/v1beta1
metadata:
  name: example
  annotations:
    kubernetes.io/ingress.class: "azure/application-gateway"
    appgw.ingress.kubernetes.io/http-cookie-based-affinity: "false"
    appgw.ingress.kubernetes.io/http-connection-draining: "true"
    appgw.ingress.kubernetes.io/http-request-timeout: "30"

[asridharan]

Thanks for the feature ask @Jawshua

[akshaysngupta]

@Jawshua It would be great if you can try out 0.6.0-rc1 and give us feedback. We will do the 0.6.0 release shortly!

[asridharan]

@markDNL @simonscatalyst @peterspicer-catalyst

@Jawshua It would be great if you can try out 0.6.0-rc1 and give us feedback. We will do the 0.6.0 release shortly!

[MarkDNL]

Great, I hope I can give it a try soon!