Fix google_bigquery_analytics_hub_listing_subscription import (#15331)

Author: wj-chen

mmv1/products/bigqueryanalyticshub/ListingSubscription.yaml

@@ -32,6 +32,7 @@ import_format:
 custom_code:
   decoder: 'templates/terraform/decoders/bigqueryanalyticshub_listing_subscription.go.tmpl'
   pre_read: 'templates/terraform/pre_read/bigqueryanalyticshub_listing_subscription.tmpl'
+  post_read: 'templates/terraform/post_read/bigqueryanalyticshub_listing_subscription.go.tmpl'
   pre_delete: 'templates/terraform/pre_read/bigqueryanalyticshub_listing_subscription.tmpl'
   post_import: templates/terraform/post_import/analytics_hub_subscription.go.tmpl
 sweeper:
@@ -76,7 +77,6 @@ properties:
   - name: 'destinationDataset'
     type: NestedObject
     required: true
-    ignore_read: true
     description:
       The destination dataset for this subscription.
     properties:

mmv1/templates/terraform/post_read/bigqueryanalyticshub_listing_subscription.go.tmpl

@@ -0,0 +1,12 @@
+// Set data_exchange_id and listing_id from res["listing"]
+listing := res["listing"].(string)
+parts := strings.Split(listing, "/")
+if len(parts) != 8 {
+	return fmt.Errorf("Listing name %q is not in the expected format projects/*/locations/*/dataExchanges/*/listings/*", listing)
+}
+if err := d.Set("data_exchange_id", parts[5]); err != nil {
+  return fmt.Errorf("Error reading ListingSubscription: %s", err)
+}
+if err := d.Set("listing_id", parts[7]); err != nil {
+  return fmt.Errorf("Error reading ListingSubscription: %s", err)
+}