Add injected credentials tab (#1295)

* chore: 🤖 introduce injected application credentials on the UI

addons/api/addon/models/credential.js

@@ -1,3 +1,10 @@
 import GeneratedCredentialModel from '../generated/models/credential';
+import { equal } from '@ember/object/computed';
 
-export default class CredentialModel extends GeneratedCredentialModel {}
+export default class CredentialModel extends GeneratedCredentialModel {
+  // =attributes
+  /**
+   * @type {boolean}
+   */
+  @equal('type', 'username_password') isUsernamePassword;
+}