crate-header: Load crate.keywords explicitly with a task

This fixes the following deprecation warning:
- Do not use A() on an EmberData PromiseManyArray.

Author: eth3lbert

app/components/crate-header.hbs

@@ -24,9 +24,9 @@
     </div>
   {{/if}}
 
-  {{#if @crate.keywords}}
+  {{#if this.keywords}}
     <ul local-class="keywords">
-      {{#each @crate.keywords as |keyword|}}
+      {{#each this.keywords as |keyword|}}
         <li>
           <LinkTo @route="keyword" @model={{keyword.id}} data-test-keyword={{keyword.id}}>
             <span local-class="hash">#</span>{{keyword.id}}

app/components/crate-header.js

@@ -1,10 +1,27 @@
 import { inject as service } from '@ember/service';
 import Component from '@glimmer/component';
 
+import { task } from 'ember-concurrency';
+import { alias } from 'macro-decorators';
+
 export default class CrateHeader extends Component {
   @service session;
 
+  @alias('loadKeywordsTask.last.value') keywords;
+
+  constructor() {
+    super(...arguments);
+
+    this.loadKeywordsTask.perform().catch(() => {
+      // ignore all errors and just don't display keywords if the request fails
+    });
+  }
+
   get isOwner() {
     return this.args.crate.owner_user.findBy('id', this.session.currentUser?.id);
   }
+
+  loadKeywordsTask = task(async () => {
+    return (await this.args.crate?.keywords) ?? [];
+  });
 }