Support Managed Identity for Image ACR pulling in App Service image update command

[yurymalash]

Related command

az webapp config container set -g my-resource_group -n my-web-app -c my-acr.azurecr.io/myimage:1.0.0 -r https://my-acr.azurecr.io

Is your feature request related to a problem? Please describe.

Current implementation only supports ACR username and password which is not the safest approach.
See method 'update_container_settings' at line 2195 https://github.com/Azure/azure-cli/blob/dev/src/azure-cli/azure/cli/command_modules/appservice/custom.py

There is no provisioning for authentication to ACR using managed identity.
This is especially annoying considering the fact that Managed Identity is supported in general for App Service ACR pull.

Describe the solution you'd like

'az webapp config container set ' command to use Managed Identity for ACR authentication

Describe alternatives you've considered

I cannot find alternative of the image update without getting back to infra deployment, e.g. Terraform infra supplying the image details. I need more robust way of image update.

Additional context

[yonzhan]

Thank you for opening this issue, we will look into it.

[seligj95]

Resolved by: #30855