Support for azurerm_application_gateway PrivateLink attributes

[geertn]

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Description

In Azure you can create a Private Link Service on an Application Gateway and after that, create a Private Endpoint to the PLS using the following construct:

resource "azurerm_private_endpoint" "pe" {
  name                = "${local.name_prefix}-gw-pe"
  location            = azurerm_resource_group.rg.location
  resource_group_name = azurerm_resource_group.rg.name
  subnet_id           = data.azurerm_subnet.mgmt.id

  private_service_connection {
    name                           = "${local.name_prefix}-xxx-pe"
    private_connection_resource_id = "/subscriptions/xxx/resourceGroups/rg/providers/Microsoft.Network/applicationGateways/waf-apigw"
    is_manual_connection = false
    subresource_names = [
      "apigw-feip01"
    ]
  }
}

However Terraform azurerm provider doesn't support setting the Private Link configuration.

Azure CLI has the ability to add a Private Link Resource to the Application Gateway:
https://docs.microsoft.com/en-us/cli/azure/network/application-gateway/private-link?view=azure-cli-latest#az_network_application_gateway_private_link_add
https://github.com/Azure/azure-cli/blob/dev/src/azure-cli/azure/cli/command_modules/network/custom.py#L475

REST API has support too:
https://docs.microsoft.com/en-us/rest/api/application-gateway/applicationgateways/createorupdate#request-body
https://docs.microsoft.com/en-us/rest/api/application-gateway/applicationgateways/createorupdate#applicationgatewayprivatelinkconfiguration

GoSDK seems to have support too:
https://github.com/Azure/azure-sdk-for-go/blob/071e3dc47fba538f4d7bcd482a320b699c89812f/services/network/mgmt/2020-05-01/network/applicationgatewayprivatelinkresources.go

ARM/Bicep:
https://docs.microsoft.com/en-us/azure/templates/microsoft.network/applicationgateways?tabs=bicep

New or Affected Resource(s)

• azurerm_application_gateway

Potential Terraform Configuration

# Copy-paste your Terraform configurations here - for large Terraform configs,
# please use a service like Dropbox and share a link to the ZIP file. For
# security, you can also encrypt the files using our GPG public key.

I'd like to reference to the Bicep example

References

• #0000