## Is your feature request related to a problem?

When sending incorrectly formatted payloads (e.g. a text-based string with a `gzip` compression header), the app will fail with a cryptic 500 error and register an unhandled exception.

## Describe the solution you'd like
The app should return a 400 bad request error, with details on why the request failed (i.e. it is incorrectly formatted or the content does not match the compression specified). In addition, this shouldn't be treated as an unhandled exception as it's a client error.


## Describe alternatives you've considered
Keep returning a cryptic 500 error.


## Additional context
Relevant context on #2701


#### *Thank you* for your feature request – we love each and every one!

posthog/settings.py
value = os.getenv(key)
    if value is None:
        if optional:
            return None
        if default is not None:
            return default
        else:
            raise ImproperlyConfigured(f'The environment variable "{key}" is required to run PostHog!')
    if type_cast is not None:
        return type_cast(value)
    return value
def get_list(text: str) -> List[str]:
    if not text:
        return []
    return [item.strip() for item in text.split(",")]
def print_warning(warning_lines: Sequence[str]):
    highlight_length = min(max(map(len, warning_lines)) // 2, shutil.get_terminal_size().columns)
    print("\n".join(("", "🔻" * highlight_length, *warning_lines, "🔺" * highlight_length, "",)), file=sys.stderr)
# Build paths inside the project like this: os.path.join(BASE_DIR, ...)
BASE_DIR = os.path.dirname(os.path.dirname(os.path.abspath(__file__)))
DEBUG = get_from_env("DEBUG", False, type_cast=strtobool)
TEST = (
    "test" in sys.argv or sys.argv[0].endswith("pytest") or get_from_env("TEST", False, type_cast=strtobool)
)  # type: bool
E2E_TESTING = get_from_env(