Azure App Service: User-Assigned Managed Identity not automatically configured in Deployment Center via Bicep

Hi,

I am deploying an Azure App Service using Bicep (Infrastructure as Code). I am assigning a User-Assigned Managed Identity (UMI) to the App Service, and I expect the Deployment Center to automatically use this UMI for pulling container images from my Azure Container Registry.

However, even though the UMI is correctly assigned to the App Service (I can verify this in the "Identity" blade), the Deployment Center does not automatically select the UMI. I have to manually select the UMI (from the dropdown) in the Deployment Center's "Registry Settings" and save it for the App Service to function correctly.

This manual step defeats the purpose of using Infrastructure as Code. I need a way to configure the Deployment Center's UMI selection through Bicep. In the following code snippet I have the relevant properties only.

resource resAppService 'Microsoft.Web/sites@2024-04-01' = {
  name: appServiceName
  location: location
  kind: appServiceKind
  identity: {
    type: 'UserAssigned'
    userAssignedIdentities: {
      ‘${userManagedIdentityId}': {}
    }
  }
  properties: {
      siteConfig: {
        acrUserManagedIdentityID: userManagedIdentityId  // This seems to be ignored for Deployment Center
      }
    }
}

I'm using the acrUserManagedIdentityID property in the siteConfig, which seems like it should do the trick, but it doesn't. The UMI is assigned to the App Service, but the Deployment Center doesn't pick it up automatically.

Has anyone else encountered this? Is there a way to configure the Deployment Center's UMI selection through Bicep? I'm trying to avoid any manual steps after the deployment.

I've looked through the Bicep documentation, but I haven't found a clear solution. Any help or pointers would be greatly appreciated!