…#1594)

People where complaining (rightly so) that just raising an error when SentryAsgiMiddleware and Starlette/Fastapi is used is not a nice thing to do.

So we tried again to make this work together. To not break our users code.
The plan was to make SentryASGIMiddleware no-op when there is already one there. Turns out this works already on Starlette but on FastAPI it broke. (This was because of how FastAPI deals with middlewares)

We debugged the whole thing and it turns out that we where patching our own SentryAsgiMiddleware (like the FastAPI internal ones) to create spans when they are executed. This and the fact that we use __slots__ extensively made the integration break.

We found out, that if we are not patching our own middleware this fixes the problem when initializing the middleware twice (once by our users and once by our auto-enabled FastAPI integration).

Fixes #1592