Remove records from the store when they are no longer in array responses

Ember Data doesn't do this by default, instead opting to be as
non-destructive as possible. However, this is desired behavior.

ui/app/serializers/application.js

@@ -1,3 +1,5 @@
+import { copy } from '@ember/object/internals';
+import { get } from '@ember/object';
 import { makeArray } from '@ember/array';
 import JSONSerializer from 'ember-data/serializers/json';
 
@@ -35,8 +37,29 @@ export default JSONSerializer.extend({
           documentHash.included.push(...included);
         }
       });
+    });
 
-      store.push(documentHash);
+    store.push(documentHash);
+  },
+
+  normalizeArrayResponse(store, modelClass) {
+    const result = this._super(...arguments);
+    this.cullStore(store, modelClass.modelName, result.data);
+    return result;
+  },
+
+  // When records are removed server-side, and therefore don't show up in requests,
+  // the local copies of those records need to be unloaded from the store.
+  cullStore(store, type, records) {
+    const newRecords = copy(records).filter(record => get(record, 'id'));
+    const oldRecords = store.peekAll(type);
+    oldRecords.filter(record => get(record, 'id')).forEach(old => {
+      const newRecord = newRecords.find(record => get(record, 'id') === get(old, 'id'));
+      if (!newRecord) {
+        store.unloadRecord(old);
+      } else {
+        newRecords.removeObject(newRecord);
+      }
     });
   },