STCOR-798 fully populate /bl-users/_self API response in tests (#1401)

Provide a fully-populated user object, instead of an empty one, from
`/bl-users/_self` in tests. Tests that expect an authenticated user may
fail if they end up calling the endpoint and don't receive the expected
data. It's unclear exactly why we're hitting this glitch now, but here
we are. 🤷

h/t @JohnC-80 for figuring this out. He deserves the credit here; I'm
just the codemonkey who happened to be available to implement his
suggested fix.

Refs STCOR-798

test/bigtest/network/config.js

@@ -44,7 +44,33 @@ export default function configure() {
     configs: []
   });
 
-  this.get('/bl-users/_self', {});
+  this.get('/bl-users/_self', {
+    'user': {
+      'username': 'diku_admin',
+      'id': '882c886a-2d9a-5ffa-afc5-13912c257b99',
+      'active': true,
+      'patronGroup': '3684a786-6671-4268-8ed0-9db82ebca60b',
+      'proxyFor': [
+      ],
+      'personal': {
+        'lastName': 'ADMINISTRATOR',
+        'firstName': 'DIKU',
+        'email': '[email protected]',
+        'addresses': [
+        ]
+      },
+      'createdDate': '2024-01-22T01:55:50.661+00:00',
+      'updatedDate': '2024-01-22T01:55:50.661+00:00',
+      'metadata': {
+        'createdDate': '2024-01-22T01:52:08.076+00:00',
+        'updatedDate': '2024-01-22T01:55:50.656+00:00',
+        'updatedByUserId': '882c886a-2d9a-5ffa-afc5-13912c257b99'
+      },
+      'departments': [
+      ]
+    }
+  });
+
   this.post('/bl-users/password-reset/validate', () => {
     return new Response(204, {}, '');
   });