Chore: Decrease backend test suite time (a little) (#14213)

* Chore: Speed up test setup by hashing passwords with MD5 and batching index writes

Don't use Django's default PBKDF2, about 600 ms per use and 110 uses across the suite. Switches to MD5 instead.

Also fixes a test that didn't batch update the search index

* Chore: Stop the invalid webhook params test from waiting on a Celery broker

test_workflow_webhook_action_url_invalid_params_headers left send_webhook.apply_async unpatched, so it tried to actually enqueu and waited for the timeout.

src/documents/tests/search/test_documented_syntax.py

@@ -269,7 +269,7 @@ class TestDocumentedDateForms:
             yield
 
     @pytest.fixture
-    def dated(self, index_document: Callable[..., Document]) -> dict[str, int]:
+    def dated(self, backend: TantivyBackend) -> dict[str, int]:
         stamps = {
             "today": datetime(2026, 6, 15, 9, 0, tzinfo=UTC),
             "yesterday": datetime(2026, 6, 14, 9, 0, tzinfo=UTC),
@@ -279,14 +279,14 @@ class TestDocumentedDateForms:
             "january": datetime(2026, 1, 10, 10, 0, tzinfo=UTC),
             "old": datetime(2005, 3, 4, 15, 30, tzinfo=UTC),
         }
-        return {
-            label: index_document(
-                title=label,
-                content="dated body",
-                added=stamp,
-            ).pk
+        docs = {
+            label: DocumentFactory(title=label, content="dated body", added=stamp)
             for label, stamp in stamps.items()
         }
+        with backend.batch_update() as batch:
+            for doc in docs.values():
+                batch.add_or_update(doc)
+        return {label: doc.pk for label, doc in docs.items()}
 
     @pytest.mark.parametrize(
         ("query", "label"),