Revert "fix(api): infer /documents/{id}/download Content-Type from filename when ext is omitted (#15052)" (#15138)

Reverts infiniflow/ragflow#15053

test/testcases/test_web_api/test_document_app/test_document_metadata.py

@@ -420,11 +420,6 @@ class TestDocumentMetadataUnit:
 
         # From here on the user is authorized; exercise the original branches.
         monkeypatch.setattr(module.DocumentService, "accessible", lambda _doc_id, _user_id: True)
-        monkeypatch.setattr(
-            module.DocumentService,
-            "get_by_id",
-            lambda _doc_id: (True, SimpleNamespace(name="stub.bin", type=module.FileType.OTHER.value)),
-        )
 
         async def fake_thread_pool_exec(*_args, **_kwargs):
             return b"attachment"
@@ -446,18 +441,6 @@ class TestDocumentMetadataUnit:
         assert res.headers["content_type"] == "application/abc"
         assert res.headers["extension"] == "abc"
 
-        # No `ext` query param: infer MIME/extension from the stored document filename (aligned with /preview).
-        monkeypatch.setattr(module, "request", _DummyRequest(args={}))
-        monkeypatch.setattr(
-            module.DocumentService,
-            "get_by_id",
-            lambda _doc_id: (True, SimpleNamespace(name="Annual report.PDF", type=module.FileType.PDF.value)),
-        )
-        res = _run(module.download_attachment(attachment_id="att1"))
-        assert isinstance(res, _DummyResponse)
-        assert res.headers["content_type"] == "application/pdf"
-        assert res.headers["extension"] == "pdf"
-
         async def raise_error(*_args, **_kwargs):
             raise RuntimeError("download boom")