[BUG] SessionSharing doesn't work on Windows - shared memory destroyed after handle closed

[swatmaps]

Describe the bug

SessionSharingThread creates shared memory but immediately closes the handle in _share_token(). On Windows, shared memory is destroyed when all handles are closed, so worker processes cannot access it.

To Reproduce

Environment

• OS: Windows 10/11
• Python: 3.12
• sentinelhub-py: 3.11.x

Steps to Reproduce

from concurrent.futures import ProcessPoolExecutor
from sentinelhub import SentinelHubSession, SHConfig
from sentinelhub.download import SessionSharing, collect_shared_session

def worker():
    session = collect_shared_session()
    return session.token["access_token"][:20]

config = SHConfig()
# config.sh_client_id = "..."
# config.sh_client_secret = "..."

session = SentinelHubSession(config)

with SessionSharing(session), ProcessPoolExecutor(max_workers=1) as executor:
    future = executor.submit(worker)
    print(future.result())

Expected Behavior

Worker processes should be able to access the shared session token.

Actual Behavior

FileNotFoundError: [WinError 2] The system cannot find the file specified: 'sh-session-token'

Root Cause

In _share_token(), the shared memory handle is closed after writing:

def _share_token(self, token: JsonDict) -> None:
    encoded_token = json.dumps(token).encode()
    memory = self._get_shared_memory(encoded_token)

    try:
        memory.buf[:] = encoded_token + _NULL_MEMORY_VALUE * (memory.size - len(encoded_token))
    finally:
        memory.close()  # <-- This destroys the memory on Windows