I want the ability to add both Artifact Registry and Upstream Proxy as an Upstream Proxies in an existing Artifact Registry.

My use case is that we have our internal artifacts being published to an Artifact Registry and a Upstream Proxy for public artifacts.

My requirement is to create a single Artifact Registry that serves as a group/proxy to both our internal and public registries. However, I'm not able to do this in Harness as a result of only being to add Upstream Proxy registries to Upstream Proxies in an existing Artifact Registry.