Add a property for the full gallery ID to the shared_image_gallery block

[danbarr]

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Description

Currently, the shared_image_gallery block has individual properties for the elements of an Azure Compute Gallery's ID: subscription, resource_group, gallery_name, image_name, image_version.

But when referencing a source/parent image from HCP Packer, the hcp-packer-artifact data source's external_identifier returns the full ID string, /subscriptions/<id>/resourceGroups/<name>/providers/Microsoft.Compute/galleries/<name>/images/<name>/versions/<version>

This means we have to do some nasty & fragile string parsing to pull out the individual components, or use the build labels from the HCP Packer artifact like this:

  # Source image
  shared_image_gallery {
    subscription   = var.az_subscription_id
    resource_group = data.hcp-packer-artifact.example.labels.sig_resource_group
    gallery_name   = data.hcp-packer-artifact.example.labels.sig_name
    image_name     = data.hcp-packer-artifact.example.labels.sig_image_name
    image_version  = data.hcp-packer-artifact.example.labels.sig_image_version
  }

Propose the addition of a shared_image_gallery_id attribute which can be used in lieu of the five individual attributes, similar to the existing community_gallery_image_id and direct_shared_gallery_image_id attributes.

Use Case(s)

Integrating with HCP Packer to resolve a source image that is located in a Compute Gallery.

Potential configuration

  # Source image
  shared_image_gallery {
    shared_image_gallery_id = data.hcp-packer-artifact.example.external_identifier
  }