feat(redis): add native JSON session storage for 4.1.0

- Add opt-in SESSION_REDIS_JSON storage for asyncio Redis backends.
- Check JSON command support at startup and reject JSON mode on Trio.
- Read legacy strings and migrate sessions on their next save.
- Validate JSON objects before transactional replacement and expiry.
- Preserve tagged serialization for datetime, tuple, and other types.
- Cover command contracts, error handling, and session round-trips.
- Document server requirements, permissions, and migration limits.
- Normalize indentation and whitespace across code, tests, and examples.
- Bump the package and lockfile to 4.1.0 and update the changelog.
- Refresh the locked pycparser dependency to 3.12.

quart_session/redis_json.py

@@ -0,0 +1,37 @@
+"""Native JSON storage for the asyncio Redis session backend."""
+
+import json
+
+async def check_support(backend):
+  """Fail at startup rather than silently falling back to string storage."""
+  commands = await backend.execute_command("COMMAND", "INFO", "JSON.GET", "JSON.SET")
+  entries = list(commands.values()) if isinstance(commands, dict) else commands
+  if len(entries) != 2 or not all(entries):
+    raise RuntimeError("SESSION_REDIS_JSON requires JSON.GET and JSON.SET support")
+
+async def get(backend, key):
+  """Read legacy strings as well as native JSON documents."""
+  from redis.exceptions import ResponseError
+
+  try:
+    return await backend.get(key)
+  except ResponseError as error:
+    if not str(error).startswith("WRONGTYPE"):
+      raise
+    # A single root path returns the object, not a JSONPath result array.
+    return await backend.execute_command("JSON.GET", key, ".")
+
+async def set(backend, key, value, expiry):
+  """Replace a string or JSON key and apply expiry in one transaction."""
+  # Validate before deleting an existing key. Preserve TaggedJSONSerializer's
+  # representation so tuples, datetimes, etc. still round-trip normally.
+  document = json.loads(value)
+  if not isinstance(document, dict):
+    raise ValueError("Native Redis JSON sessions require a JSON object")
+  async with backend.pipeline(transaction=True) as pipeline:
+    pipeline.delete(key)
+    pipeline.execute_command("JSON.SET", key, "$", value)
+    if expiry is not None:
+      pipeline.expire(key, expiry)
+    results = await pipeline.execute()
+  return results[1]