azure-cli: postgres flexible-server create doesn't use an existing vnet if it's in a different resource group

When running az postgres flexible-server create and supplying --vnet and --subnet parameters for a vnet that is deployed in a different resource group, the command tries to create a new vnet and subnet in the same resource group as the server.

In many enterprise environments, the management of network resources are handled by a different team from the one that deploys application resources. This bug was discovered because the CI/CD pipeline service principal that is used to create the PostgreSQL server didn’t have permissions to create a vnet. I’ve reproduced the issue below in my own subscription, where I do have the necessary permissions, so the vnet gets created in the server resource group rather than using the existing one.

Adding a new parameter, --vnet-resource-group, and using this for the vnet would solve this problem.

Errors: Doesn’t use existing vnet.

To Reproduce:

az group create -l westeurope -n postgres-test-server-rg az group create -l westeurope -n postgres-test-vnet-rg az network vnet create --resource-group postgres-test-vnet-rg --name postgres-vnet --address-prefix 10.0.0.0/16 --subnet-name postgres-subnet --subnet-prefix 10.0.0.0/24 az postgres flexible-server create -l westeurope -n larslindpostgrestestserver -g postgres-test-server-rg --subnet postgres-subnet --vnet postgres-vnet OUTPUT: Command group ‘postgres flexible-server’ is in preview and under development. Reference and support levels: https://aka.ms/CLI_refstatus Checking the existence of the resource group ‘postgres-test-server-rg’… Resource group ‘postgres-test-server-rg’ exists ? : True You have supplied a Vnet and Subnet name. Verifying its existence… Creating new Vnet “postgres-vnet” in resource group “postgres-test-server-rg” Creating new Subnet “postgres-subnet” in resource group “postgres-test-server-rg” Creating PostgreSQL Server ‘larslindpostgrestestserver’ in group ‘postgres-test-server-rg’…

Expected Behavior

Existing vnet and subnet would be used even if the vnet is in a different resource group.

Environment Summary

Linux-4.15.0-1113-azure-x86_64-with-debian-10.2 (Cloud Shell)
Python 3.6.10
Installer: DEB

azure-cli 2.22.0 *

Extensions:
resource-graph 0.1.8
azure-iot 0.9.2
ai-examples 0.2.5
ssh 0.1.4

Additional Context