AGIC pod cannot update App Gateways with a custom 400 page set.

[cailyoung]

Describe the bug
AGIC 1.8.1 cannot update App Gateways that have a custom error set on response code 400. The activity log shows this error:

Custom error page has an invalid HTTP status code '400'

It's highly likely that this is due to using a very old version of the Go SDK for Azure:

application-gateway-kubernetes-ingress/pkg/azure/client.go

Line 15 in c6b8a31

n "github.com/Azure/azure-sdk-for-go/services/network/mgmt/2021-03-01/network"

Azure support indicated that Network API 2022-09-01 or later should work.

I note that the Azure SDK for Go says that the Go SDK version in use was deprecated at least 2 years ago. This may be a more involved update that just bumping the dependency.

To Reproduce
Steps to reproduce the behavior:

• Set a custom error page on response code 400 on an App Gateway
• Induce a reconcile (scale up a deployment, for example)

Ingress Controller details
We are using the AKS add-on, which on k8s 1.33.2 is running AGIC container version 1.8.1

• Any Azure support tickets associated with this issue.

Support ticket: 2509200030000147 was opened but couldn't resolve the issue other than by us removing the custom error page.

[cailyoung]

Support ticket 2510230030000073 opened.