403 when using special characters

Issue: When using special characters like "ö" app_handler.handle(request) will return Unauthorized.

Tools: I'm using FastAPI AsyncSlackRequestHandler adapter. I don't know if this happends in without adapters on others, this is my use case.

With this code can be reproduced: https://github.com/slackapi/bolt-python/blob/main/examples/fastapi/async_app.py

Simply using the mention listener and as a user on slack send a special character, 403 will be returned.

Hypothesis: I believe is the way the raw body is handled, that when using special characters is not well decoded or something, I'll keep looking to see if I find a solution, in the meantime reporting this as issue since seems pretty clear is one

Commencez par examples/fastapi/async_app.py et le chemin FastAPI AsyncSlackRequestHandler utilisé par app_handler.handle(request). Reproduisez le listener de mention avec un message contenant « ö » et comparez-le à un message ASCII tout en retraçant le traitement du raw body. C’est terminé lorsque les messages contenant des caractères spéciaux ne renvoient plus 403, tandis que le traitement normal des requêtes continue de fonctionner.