Include $api_base_url and $instance_url in Xano-Generated Environment Variables

Inclusion of the base URL for the current API Group (e.g., x3nq-doij-wnjei.f3p.xano.io/api:qfExeuTx) in the Xano-generated environment variables. This would help dynamically reference the API group URL in function stacks without hardcoding it.

Suggested Variable: $api_base_url

Also, including the $instance_url would be useful (e.g., x3nq-doij-wnjei.f3p.xano.io)