Background

This issue tracks the ability to reference existing resources in azure.yaml.

For example, the schema could look something like:

resources:
  existing-db:
    existing: true
    resourceId: <resource ID> # Virtual -- stored in `.env` for cross-env purposes

This enhancement builds on top of the idea that azure.yaml is representing the app-centric view of the infrastructure resources. Similar to a SQL view, resources can either be created (materialized in SQL terms) or existing (queried from in SQL terms).

Scenarios

When this type of reference metadata is present, scenarios we would want to enable for overall consistency of the system:

1. use binding relationships works with existing resources. We could imagine that environment variables are established in the same way a created resource does. This would require updating the infra synthesis to account for existing declarations.
2. Command gestures like show works with existing resources. This change would be a minimal addition of the currently established design, that each resource maps to an AZURE_RESOURCE_xx_ID upon provisioning. See compose: show <resource> #4534 for details.