feat: 🎸 add API support for user accounts

addons/api/addon/serializers/user.js

@@ -0,0 +1,33 @@
+import ApplicationSerializer from './application';
+
+export default class UserSerializer extends ApplicationSerializer {
+  // =methods
+
+  /**
+   * If `adapterOptions.accountIDs` is set (to an array of user IDs),
+   * then the payload is serialized via `serializewithAccounts`.
+   * @override
+   * @param {Snapshot} snapshot
+   * @return {object}
+   */
+  serialize(snapshot) {
+    let serialized = super.serialize(...arguments);
+    const accountIDs = snapshot?.adapterOptions?.accountIDs;
+    if (accountIDs) serialized =
+      this.serializewithAccounts(snapshot, accountIDs);
+    return serialized;
+  }
+
+  /**
+   * Returns a payload containing only the `account_ids` array (and version).
+   * @param {Snapshot} snapshot
+   * @param {[string]} account_ids
+   * @return {object}
+   */
+  serializewithAccounts(snapshot, account_ids) {
+    return {
+      version: snapshot.attr('version'),
+      account_ids,
+    };
+  }
+}