Hypercorn

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* Add a max keep alive requests configuration option, this mitigates
the HTTP/2 rapid reset attack.
* Return subprocess exit code if non-zero.
* Add ProxyFix middleware to make it easier to run Hypercorn behind a
proxy.
* Support restarting workers after max requests to make it easier to
manage memory leaks in apps.
* Bugfix ensure the idle task is stopped on error.
* Bugfix revert autoreload error because reausing old sockets.
* Bugfix send the hinted error from h11 on RemoteProtocolErrors.
* Bugfix handle asyncio.CancelledError when socket is closed without
flushing.
* Bugfix improve WSGI compliance by closing iterators, only sending
headers on first response byte, erroring if ``start_response`` is
not called, and switching wsgi.errors to stdout.
* Don't error on LocalProtoclErrors for ws streams to better cope with
race conditions.

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* Improve the NoAppError to help diagnose why the app has not been
found.
* Log cancelled requests as well as successful to aid diagnositics of
failures.
* Use more modern asyncio apis. This will hopefully fix reported
memory leak issues.
* Bugfix only load the application in the main process if the reloader
is being used.
* Bugfix Autoreload error because reausing old sockets.
* Bugfix scope client usage for sock binding.
* Bugfix disable multiprocessing if number of workers is 0 to support
systems that don't support multiprocessing.

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* Bugfix Use tomllib/tomli for .toml support replacing the
unmaintained toml library.
* Bugfix server hanging on startup failure.
* Bugfix close websocket with 1011 on internal error (1006 is a
client-only code).
* Bugfix support trio > 0.22 utilising exception groups (note trio <=
0.22 is not supported).
* Bugfix except ConnectionAbortedError which can be raised on Windows
machines.
* Bugfix ensure that closed is sent on reading end.
* Bugfix handle read_timeout exception on trio.
* Support and test against Python 3.11.
* Add explanation of PicklingErrors.
* Add config option to pass raw h11 headers.

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* Revert Preserve response headers casing for HTTP/1 as this breaks
ASGI frameworks.
* Bugfix stream WSGI responses

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* Bugfix add missing ASGI version to lifespan scope.
* Bugfix preserve the HTTP/1 request header casing through to the ASGI
app.
* Bugifx ensure the config loglevel is respected.
* Bugfix ensure new processes are spawned not forked.
* Bugfix ignore dunder vars in config objects.
* Bugfix clarify the subprotocol exception.

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* Fix Python3.7 compatibility.