tests/live: Add conftest for injecting wsn header in live tests

- Introduced `conftest.py` to the `tests/live` folder to facilitate header
  injection for live tests.
- Added `pdfrest_live_wsn` fixture to retrieve the `wsn` value from
  environment variables with a default fallback.
- Used `monkeypatch` to modify `PdfRestClient` and `AsyncPdfRestClient`
  constructors for seamless `wsn` header injection.

Assisted-by: Codex

Author: datalogics-kam

tests/live/conftest.py

@@ -0,0 +1,58 @@
+from __future__ import annotations
+
+import os
+from typing import Any
+
+import pytest
+
+from pdfrest import AsyncPdfRestClient, PdfRestClient
+
+DEFAULT_LIVE_WSN = "dl-internal-python-ci"
+
+
+def _with_live_wsn_header(kwargs: dict[str, Any], wsn: str) -> dict[str, Any]:
+    new_kwargs = dict(kwargs)
+    headers = dict(new_kwargs.get("headers") or {})
+    headers["wsn"] = wsn
+    new_kwargs["headers"] = headers
+    return new_kwargs
+
+
+@pytest.fixture(scope="session")
+def pdfrest_live_wsn() -> str:
+    return os.getenv("PDFREST_LIVE_WSN", DEFAULT_LIVE_WSN)
+
+
+@pytest.fixture(autouse=True)
+def inject_live_test_wsn_header(
+    monkeypatch: pytest.MonkeyPatch,
+    pdfrest_live_wsn: str,
+) -> None:
+    original_sync_init = PdfRestClient.__init__
+    original_async_init = AsyncPdfRestClient.__init__
+
+    def sync_init_with_live_header(
+        self: PdfRestClient,
+        *args: Any,
+        **kwargs: Any,
+    ) -> None:
+        original_sync_init(
+            self,
+            *args,
+            **_with_live_wsn_header(kwargs, pdfrest_live_wsn),
+        )
+
+    def async_init_with_live_header(
+        self: AsyncPdfRestClient,
+        *args: Any,
+        **kwargs: Any,
+    ) -> None:
+        original_async_init(
+            self,
+            *args,
+            **_with_live_wsn_header(kwargs, pdfrest_live_wsn),
+        )
+
+    monkeypatch.setattr(PdfRestClient, "__init__", sync_init_with_live_header)
+    monkeypatch.setattr(AsyncPdfRestClient, "__init__", async_init_with_live_header)
+    return