[Feature] Allow the import of a subscription by its ID

[culpinnis]

What problem are you facing?

I want to observe subscriptions that were not created by Terraform or Crossplane. My objective is to read the subscription based on its ID and get the display name to push it to a 3rd party system outside of Azure. Terraform offers the subscription data source which just needs the subscription ID.
The current implementation of the observe management policy is the same as a Terraform import. An import requires the name of a subscription alias (and requires you to create such an alias for importing the resource) for the external-name label. See the import section of the subscription resource for more information. I understand that technically an import is necessary because the management policy can change be changed at any time, but the functionality of a data only resource is missing - especially if the implemented Terraform data sources are using different API endpoints / resource identifiers to retrieve the data.

What could help solve your problem?

Allowing an import of subscriptions without having an alias created for them as the Terraform data resource is doing it.

I know that this is maybe an upstream issue for Crossplane itself.