Make content follow the version

- store content per version
- root doc retrieval returns latest content
- updating content affects the latest version
- load metadata per version

src/documents/tests/test_consumer.py

@@ -745,6 +745,7 @@ class TestConsumer(
         assert version.original_filename is not None
         self.assertEqual(version.version_label, "v2")
         self.assertTrue(version.original_filename.endswith("_v0.pdf"))
+        self.assertTrue(bool(version.content))
 
     @mock.patch("documents.consumer.load_classifier")
     def testClassifyDocument(self, m) -> None: