DCGW: TF how to for creating a network

## Jobs to be done (optional)

## Definition of done
- TF how to for creating a network https://github.com/Kong/terraform-provider-konnect/blob/main/examples/scenarios/cloud-gateways.tf

## Information
https://app.kapa.ai/93b55f65-cffb-4d0b-9da7-c8915a838dce/top-questions/clusters/1d751e26-2daa-4bee-9236-982724a556be

## Due date (optional)

## Size
L

Start with the referenced example at examples/scenarios/cloud-gateways.tf in the terraform-provider-konnect repository, then inspect the developer.konghq.com documentation structure to find the appropriate how-to location. Document the steps for creating a network with Terraform and verify that the finished guide matches the example and its intended workflow.

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