Fix: preserve document fields during Gotenberg conversion

Gotenberg's LibreOffice route enables updateIndexes by default, which
refreshes dynamic fields (e.g. auto-dates) to the current date. Disable
it so field values are preserved as authored.

src/paperless/parsers/tika.py

@@ -423,6 +423,11 @@ class TikaDocumentParser:
         logger.info("Converting %s to PDF as %s", document_path, pdf_path)
 
         with self._gotenberg_client.libre_office.to_pdf() as route:
+            # Preserve document fields as authored. updateIndexes (Gotenberg's
+            # default) triggers a refresh() that rewrites dynamic fields like
+            # auto-dates to the current date.
+            route.update_indexes(update_indexes=False)
+
             # Set the output format of the resulting PDF.
             # OutputTypeConfig reads the database-stored ApplicationConfiguration
             # first, then falls back to the PAPERLESS_OCR_OUTPUT_TYPE env var.

src/paperless/tests/parsers/test_tika_parser.py

@@ -223,4 +223,11 @@ class TestTikaParser:
 
         assert form_field_found
 
+        # Field updates must be disabled so LibreOffice preserves document
+        # fields (e.g. auto-date fields) as authored rather than refreshing
+        # them to the current date.
+        assert any(
+            b'name="updateIndexes"' in part and b"false" in part for part in parts
+        )
+
         httpx_mock.reset()