shim-airbyte-cdk: redirect rogue outputs to stdout

Some imported connectors have errant `print` calls or similar that output
directly to stdout, which Flow will otherwise interpret as a captured document
or checkpoint.

This is really ugly, but to prevent it from happening we can redirect stdout to
stderr after the task outputs have been initialized. That way the printed output
is treated as logs instead of capture data.

estuary-cdk/estuary_cdk/shim_airbyte_cdk.py

@@ -1,5 +1,7 @@
 from dataclasses import dataclass
+import io
 from logging import Logger
+import sys
 from pydantic import Field
 from typing import Any, ClassVar, Annotated, Callable, Awaitable, List, Literal
 import asyncio
@@ -294,7 +296,6 @@ async def _run(
         config: EndpointConfig,
         connector_state: ConnectorState,
     ) -> None:
-
         airbyte_streams: list[ConfiguredAirbyteStream] = [
             ConfiguredAirbyteStream(
                 stream=AirbyteStream(
@@ -336,6 +337,14 @@ async def _run(
             AirbyteStateMessage(**rs.state) for _, rs in index.values() if rs.state
         ]
 
+        # Redirect any rogue `print` or similar outputs that are sent to stdout
+        # in the airbyte code to stderr instead so that they are interpreted as
+        # logs instead of captured documents or checkpoints. It's ok to
+        # re-assign stdout like this here without keeping a reference to it
+        # because the `task` output has already captured a reference to the
+        # original stdout.
+        sys.stdout = sys.stderr
+
         for message in self.delegate.read(
             task.log, config, airbyte_catalog, airbyte_states
         ):