In #6778 we found that AWS forwards HTTP headers to Lambdas from clients without modifying their casing. Since users are relying on this behavior, it effectively renders a web server that lowercases headers unusable as proxy for localstack. In general, I think there is a case to be made that web servers should not manipulate the casing of request headers, so that they can function as application-layer proxy to backends that make assumptions about header casing.

The issue of header casing for HTTP/1.1 in hypercorn was addressed with https://github.com/pgjones/hypercorn/issues/66, but later reverted with https://github.com/pgjones/hypercorn/issues/77. Apparently the relevant ASGI spec is being discussed here https://github.com/django/asgiref/issues/246 where I think we should make that case.

If this is a fundamental limitation of ASGI and we cannot get this into hypercorn, then we will be forced to either
- apologize to lambda users and tell them that they need to re-write their lambda code in a way that treats headers in a case-insensitive way
- fork hypercorn and maintain our own version
- use another webserver that does not manipulate HTTP headers, or at least allows access to the raw headers in some way
response = await make_response("{}")
        if handler:
            data = await request.get_data()
            try:
                result = await run_sync(handler, request, data)
                if isinstance(result, Exception):
                    raise result
            except Exception as e:
                LOG.warning(
                    "Error in proxy handler for request %s %s: %s %s",
                    request.method,
                    request.url,
                    e,
                    traceback.format_exc(),
                )
                response.status_code = 500
                if isinstance(e, HTTPErrorResponse):
                    response.status_code = e.code or response.status_code
                return response
            if result is not None:
                
                async_gen = get_async_generator_result(result)
                if async_gen: