Fix allocation count in CSI volumes table (#9515)

This closes #9495. As detailed in there, the collection query GET
/v1/volumes?type=csi doesn’t return ReadAllocs and WriteAllocs, so the #
Allocs cell was always showing 0 upon first load because it was derived
from the lengths of those arrays. This uses the heretofore-ignored
CurrentReaders and CurrentWriters values to calculate the total instead.

The single-resource query GET /v1/volume/csi%2F:id doesn’t return
CurrentReaders and CurrentWriters that absence doesn’t override the
stored values when visiting an individual item.

Thanks to @apollo13 for reporting this and to @tgross for the API logs
and suggestion.

ui/app/models/volume.js

@@ -18,6 +18,14 @@ export default class Volume extends Model {
     return [...this.writeAllocations.toArray(), ...this.readAllocations.toArray()];
   }
 
+  @attr('number') currentWriters;
+  @attr('number') currentReaders;
+
+  @computed('currentWriters', 'currentReaders')
+  get allocationCount() {
+    return this.currentWriters + this.currentReaders;
+  }
+
   @attr('string') externalId;
   @attr() topologies;
   @attr('string') accessMode;

ui/app/templates/csi/volumes/index.hbs

@@ -62,7 +62,7 @@
                 ({{row.model.nodesHealthy}}/{{row.model.nodesExpected}})
               </td>
               <td data-test-volume-provider>{{row.model.provider}}</td>
-              <td data-test-volume-allocations>{{row.model.allocations.length}}</td>
+              <td data-test-volume-allocations>{{row.model.allocationCount}}</td>
             </tr>
           </t.body>
         </ListTable>

ui/mirage/serializers/csi-volume.js

@@ -14,7 +14,7 @@ export default ApplicationSerializer.extend({
   serialize() {
     var json = ApplicationSerializer.prototype.serialize.apply(this, arguments);
     if (json instanceof Array) {
-      json.forEach(serializeVolume);
+      json.forEach(serializeVolumeFromArray);
     } else {
       serializeVolume(json);
     }
@@ -22,6 +22,14 @@ export default ApplicationSerializer.extend({
   },
 });
 
+function serializeVolumeFromArray(volume) {
+  volume.CurrentWriters = volume.WriteAllocs.length;
+  delete volume.WriteAllocs;
+
+  volume.CurrentReaders = volume.ReadAllocs.length;
+  delete volume.ReadAllocs;
+}
+
 function serializeVolume(volume) {
   volume.WriteAllocs = groupBy(volume.WriteAllocs, 'ID');
   volume.ReadAllocs = groupBy(volume.ReadAllocs, 'ID');